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/diffeditor/diffeditordocument.cpp

@@ -42,7 +42,7 @@
 namespace DiffEditor {
 
 DiffEditorDocument::DiffEditorDocument() :
-    Core::TextDocument(),
+    Core::BaseTextDocument(),
     m_controller(new DiffEditorController(this))
 {
     setId(Constants::DIFF_EDITOR_ID);