update README, ChangeLog
Removed tag 5.0.2
Added tag 0.5.1 for changeset 11f3032a5cbf
Removed tag 5.0.1
Added tag 0.5.2 for changeset 20a2b8ba3e6c
MainWindow2: update title, about
Update README
format code
create .ts file
Preferences:
1. the owner of Preferences is now MainWindow2 from Editor.
2. Preferences ctor now have parent
3. add #ifndef _PREFERENCES_H_ to preference.h
Editor: delete unused code
Editor: move saveDocument(), saveForce(), saveObject() to MainWindow2
Editor: move savedName to object.strCurrentFilePath
Editor: delete unused code
MainWindow2: rename saveDocuemnt() => saveAsNewDocument()
fix compile error of #e3d46f07dd02
Editor: move maybeSave() to MainWindow2
Editor: code cleanup
minor