Add channel filtering

[moio]

Depends on #1

Add a GET parameters to filter content in a repo which is served by minima, eg.

• appending ?until=2017-08-01 to a repo URL results in a new repo which contains packages and patches published before or on August 2017
• appending ?including=CVE-2017-8386 adds patches related to CVE report 8386
• appending ?excluding=SUSE-12-SP1-2017-859 excludes updates about SUSE advisory 859