Add "..." to some menu items

Add "..." to those which will open a dailog to let user interactive before actually run the command,
"Save As" to "Save As..." for example.
Rname Help->About to About Synfig Studio
Remove some action definations from app.cpp to cleanup the app.cpp

These actions are defined in canvasview.cpp or mainwindow.cpp
Remove actoin definations from app for those actions which defined in mainwindow or canvasview
Remove action definations from app for those actions defined in canvasview
Rename Setup... menuitem to Preferences... (UI only)
Rename menu item Canvas->Properties to Properties...