VCS[Bazaar, Mercurial]: Add diff formatting, revert chunk.

Add toolbar controls for ignore-whitespace to editors
and wire 'Revert Chunk' context menus.

Fix Bazaar diff interaction (find the file on doubleclick).

Introduce initializeDiffEditor to BaseClient and wire the editors
there.

src/plugins/vcsbase/vcsbaseeditor.cpp

@@ -700,6 +700,8 @@ DiffChunk VCSBaseEditorWidget::diffChunk(QTextCursor cursor) const
         return rc;
     // Concatenate chunk and convert
     QString unicode = block.text();
+    if (!unicode.endsWith(QLatin1Char('\n'))) // Missing in case of hg.
+        unicode.append(QLatin1Char('\n'));
     for (block = block.next() ; block.isValid() ; block = block.next()) {
         const QString line = block.text();
         if (checkChunkLine(line, &chunkStart)) {