Align escaped newlines

Align all escaped newlines at column 72, like in the rest of the
Makefiles.

Don't align the icon handling stuff since it comes from another
code base.

https://bugzilla.gnome.org/show_bug.cgi?id=727688
Use real scalable icons

Use installed icons instead of including icons inside the data resource.
This makes it possible for GDk to scale the icons manually and also
seems to be the preferred way to deal with icons.

https://bugzilla.gnome.org/show_bug.cgi?id=727688