Generic icons support in shared-mime-info

[Bastien Nocera]

Heya,

It took me a while, but the ~250 mime-types that required generic-icon
(all the application/ mime-types and a bunch of others) in the
shared-mime-info database now have generic-icons added to them.

I'll release shared-mime-info 0.24 some time next week after the
translators have had time to catch up on the new strings.

I could do with more eye-balls on the changes before release, bugs
should go to the fd.o bugzilla.

Cheers