Depend on PyGObject 3.11
Stop using GObject.threads_init()

Resolves a PyGTKDeprecationWarning
Always name arguments to GObject constructors

Resolves several PyGTKDeprecationWarnings
Fix copyright sign in about dialog

Seems like the escape sequences don't work in Python 3.
About dialog: update website
Updated Lithuanian translation
Updated Greek translation
Updated Spanish translation
Updated Czech translation
Updated Brazilian Portuguese translation