Port to pygi and gdbus

* Port from pygtk to pygi
* Port from python-dbus to gdbus
* restructure code
* add (still simple) testsuite

https://bugzilla.gnome.org/show_bug.cgi?id=681093
Fix bus list filter and add filter completion
Fix close action
Add about dialog
Make introspection async and cleanup code

* use async method to introspect
* make AddressInfo class attributes private
* close the connection in the destructor
* move some ui stuff to Glade
* minor fixes
Add missing AccelGroup
Fix tests
Remove toolbar with 3 identical buttons
Remove unused timing calculation
Order bus name list
Fix Spinner handling
Don't expand the whole introspection tree
Show System/Session bus tabs on startup
Remove extra spaces in docstrings
Replace "except Exception, e" with "except Exception as e"
Remove useless super() calls
Remove tests/tests.py~
Fix GObject import
Fix reload button
Use custom sort func for bus list