Snippets: Move snippet parsing into the snippet class

* Move the code to parse snippets into the snippet class
* Allow to escape $ so that this character can be used in
  snippets
* Add unit tests for the snippet parsing

Change-Id: I134f3c0de8290e1d7fcaf808577b31f5ac8fbc63
Reviewed-by: David Schulz <david.schulz@digia.com>

src/plugins/texteditor/snippets/snippet.h

@@ -33,6 +33,7 @@
 #include <texteditor/texteditor_global.h>
 
 #include <QChar>
+#include <QList>
 #include <QString>
 
 namespace TextEditor {
@@ -67,6 +68,20 @@ public:
 
     static const QChar kVariableDelimiter;
 
+    class ParsedSnippet {
+    public:
+        QString text;
+        bool success;
+        struct Range {
+            Range(int s, int l) : start(s), length(l) { }
+            int start;
+            int length;
+        };
+        QList<Range> ranges;
+    };
+
+    static ParsedSnippet parse(const QString &snippet);
+
 private:
     bool m_isRemoved;
     bool m_isModified;