Avoid C++ string conversion warnings

Change the type of string literals to const gchar * in
ET_File_Description.
Refactor Scan_Convert_P20_Into_Space()

https://bugzilla.gnome.org/show_bug.cgi?id=726108
Set default size on image properties dialogue

This gives a better result than setting a size request on the image
types tree view.
Added Telugu initial Translation
Update supported format list in help
Add help page on ID3 tag version problems

Also see https://bugs.launchpad.net/ubuntu/+source/easytag/+bug/684352
Add help page on Ogg tag splitting
Update help now that MP4 cover art is supported