Initial port to gobject introspection

Gtk+ version is forced to 2.0, Gtk+ 3.0 support will be added later
Some fixes after testing
Some fixes after testing
Fix set_search_equal_func call for introspection
More fixes for introspection
More fixes for introspection
More fixes for introspection
Fix Gtk menu items with introspection
Update dependencies in README.md
Some fixes
Add --with-gtk argument in configure, enabling GTK3 by default
Remove has-separator properties, dropped from GTK3
Improve GTK3 support
Fix authors in about window with GTK3
Add missing Gdk import, missing issected variable and fix GTK_API_VERSION check
Functions.py: sn.set_* expects bytes not unicode.
Functions.py: fix type in previous commit
applet: Gtk3, pack_start requires expand set.
Remove all the gtk2 code
Applet menu: Fix right click