AppDB - allow maintainers to process submitted screenshots and application versions

[Chris Morgan]

This patch should offload a little bit of the work involved in being
an appdb admin by allowing maintainers and super maintainers to
process screenshots submitted for applications they maintain or
supermaintain, or to process submitted versions for applications they
super maintain.

Any comments on the code changes?  Ideas for improving the patch?  I
wanted as much review as possible for this one given that we are
expanding the roles of maintainers.

ChangeLog:
Chris Morgan 
Allow maintainers to process submitted screenshots and application
versions for applications they maintain and supermaintain.

Chris