Add a generic filter to get the message of a specific fedoraproject project

fixes https://github.com/fedora-infra/fmn.rules/issues/2
Enable the generic fedorahosted per project filter to support multiple projects
Update the generic filter for Fedora Hosted projects

This takes into account the suggestions of @ralphbean
Make sure there is no un-desired spaces
Fix the docstring to be more accurate about the function's action
Merge pull request #4 from fedora-infra/filter_hosted

Add a generic filter to get the message of a specific fedoraproject project