Rename {Core,TextEditor},{Base,}TextDocument classes

First step of some more 'Base' removal in TextEditor.
s/Core::TextDocument/Core::BaseTextDocument/
s/TextEditor::BaseTextDocument/TextEditor::TextDocument/

Change-Id: I71ba325a2f0ad72ec9dae0d96846cbae72d326f7
Reviewed-by: hjk <hjk121@nokiamail.com>

src/plugins/cppeditor/cppeditordocument.cpp

@@ -166,7 +166,7 @@ void CppEditorDocument::applyFontSettings()
             b = b.next();
         }
     }
-    BaseTextDocument::applyFontSettings(); // rehighlights and updates additional formats
+    TextDocument::applyFontSettings(); // rehighlights and updates additional formats
 }
 
 void CppEditorDocument::invalidateFormatterCache()