Import package modules on demand.

This works seamlessly (i.e. no intervent in programs using quickstart is needed).
This permits to use only parts of quickstart (e.g. quickstart.translations) without importing not needed bits (__init__.py previously imported everything in the package).

I love Python. <3
builder: made DynamicObjectsDictionary contents also attributes.

It is now possible to use something like:

self.objects.main_window.show_all()

instead of

self.objects["main_window"].show_all()

The old notation is still, of course, supported.

I love Python (again). <3
1.1.0
Merge branch 'master' into debian
debian/control: require Python 2.7+.
1.1.0-1