Improve git2lp and is_direct_release behaviour

* git2lp and is_direct_release are now functions extracted to the projects.py;
* git2lp and is_direct_release mappings are now loaded from projects.yaml;
* temporarily old mappings are used if no info found in projects.yaml.

Fixes: bug #1202820
Fixes: bug #1202800
Fixes: bug #1082792

Change-Id: I487761d110cf781acea26b997486ea24a7deb25e