Standardize header names and file locations

This is both a really big and a really small commit. It is small in
that it only contains renaming, moving and modification of include
directives caused by this.

It is really big in the obvious way of touching something like 200
files.

The new rules for naming files is simple: headers use the `.hpp`
extension. The rules for physical file layout is still kinda in
progress, but the basics are also simple:
 * Significant parts of functionality get their own subfolder
   * Benchmarking is in `catch2/benchmark`
   * Matchers are in `catch2/matchers`
   * Generators are in `catch2/generators`
   * Reporters are in `catch2/reporters`
   * Baseline testing facilities are in `catch2/`
 * Various top level folders also contain `internal` subfolder,
   with files that users probably do not want to include directly,
   at least not until they have to write something like their own
   reporter.
    * The exact files in these subfolders is likely to change later
      on

Note that while some includes were cleaned up in this commit, it
is only the low hanging fruit and further cleanup using automatic
tooling will happen later.

Also note that various include guards, copyright notices and file
headers will also be standardized later, rather than in this commit.

src/catch2/internal/catch_string_manip.cpp

@@ -0,0 +1,109 @@
+/*
+ *  Created by Martin on 25/07/2017.
+ *
+ *  Distributed under the Boost Software License, Version 1.0. (See accompanying
+ *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+
+#include <catch2/internal/catch_string_manip.hpp>
+#include <catch2/catch_stringref.hpp>
+
+#include <algorithm>
+#include <ostream>
+#include <cstring>
+#include <cctype>
+#include <vector>
+
+namespace Catch {
+
+    namespace {
+        char toLowerCh(char c) {
+            return static_cast<char>( std::tolower( c ) );
+        }
+    }
+
+    bool startsWith( std::string const& s, std::string const& prefix ) {
+        return s.size() >= prefix.size() && std::equal(prefix.begin(), prefix.end(), s.begin());
+    }
+    bool startsWith( std::string const& s, char prefix ) {
+        return !s.empty() && s[0] == prefix;
+    }
+    bool endsWith( std::string const& s, std::string const& suffix ) {
+        return s.size() >= suffix.size() && std::equal(suffix.rbegin(), suffix.rend(), s.rbegin());
+    }
+    bool endsWith( std::string const& s, char suffix ) {
+        return !s.empty() && s[s.size()-1] == suffix;
+    }
+    bool contains( std::string const& s, std::string const& infix ) {
+        return s.find( infix ) != std::string::npos;
+    }
+    void toLowerInPlace( std::string& s ) {
+        std::transform( s.begin(), s.end(), s.begin(), toLowerCh );
+    }
+    std::string toLower( std::string const& s ) {
+        std::string lc = s;
+        toLowerInPlace( lc );
+        return lc;
+    }
+    std::string trim( std::string const& str ) {
+        static char const* whitespaceChars = "\n\r\t ";
+        std::string::size_type start = str.find_first_not_of( whitespaceChars );
+        std::string::size_type end = str.find_last_not_of( whitespaceChars );
+
+        return start != std::string::npos ? str.substr( start, 1+end-start ) : std::string();
+    }
+
+    StringRef trim(StringRef ref) {
+        const auto is_ws = [](char c) {
+            return c == ' ' || c == '\t' || c == '\n' || c == '\r';
+        };
+        size_t real_begin = 0;
+        while (real_begin < ref.size() && is_ws(ref[real_begin])) { ++real_begin; }
+        size_t real_end = ref.size();
+        while (real_end > real_begin && is_ws(ref[real_end - 1])) { --real_end; }
+
+        return ref.substr(real_begin, real_end - real_begin);
+    }
+
+    bool replaceInPlace( std::string& str, std::string const& replaceThis, std::string const& withThis ) {
+        bool replaced = false;
+        std::size_t i = str.find( replaceThis );
+        while( i != std::string::npos ) {
+            replaced = true;
+            str = str.substr( 0, i ) + withThis + str.substr( i+replaceThis.size() );
+            if( i < str.size()-withThis.size() )
+                i = str.find( replaceThis, i+withThis.size() );
+            else
+                i = std::string::npos;
+        }
+        return replaced;
+    }
+
+    std::vector<StringRef> splitStringRef( StringRef str, char delimiter ) {
+        std::vector<StringRef> subStrings;
+        std::size_t start = 0;
+        for(std::size_t pos = 0; pos < str.size(); ++pos ) {
+            if( str[pos] == delimiter ) {
+                if( pos - start > 1 )
+                    subStrings.push_back( str.substr( start, pos-start ) );
+                start = pos+1;
+            }
+        }
+        if( start < str.size() )
+            subStrings.push_back( str.substr( start, str.size()-start ) );
+        return subStrings;
+    }
+
+    pluralise::pluralise( std::size_t count, std::string const& label )
+    :   m_count( count ),
+        m_label( label )
+    {}
+
+    std::ostream& operator << ( std::ostream& os, pluralise const& pluraliser ) {
+        os << pluraliser.m_count << ' ' << pluraliser.m_label;
+        if( pluraliser.m_count != 1 )
+            os << 's';
+        return os;
+    }
+
+}