Implement issue filtering by repo

[dtgay]

Currently, users can filter issues by user/organization and whether the issue is assigned to them. It would be incredibly helpful and awesome if users could also filter by a list of repo names.

For instance, I want to see issues from a the projects I'm concerned with in the fedora-infra organization. I don't want the issues from all projects, and I certainly don't want to manually assign myself to every issue in the projects I'm concerned with.

[ralphbean]

Lemme know if you have any problems with the solution, @oddshocks.

[dtgay]

Nice!