We can now select which projects should have the issue tracker enabled

also should solve #8

ow2/management-office#842 , #9

Still a lot of room for improvement...

introduced logging and added a couple of call to recordOrphan()

 ow2/management-office#831

Keeping issues_enabled until the gitlab API is fixed (#5)

start work on #5 to enable issue tracker As now GitLab API only accept true/false for issues_enabled.

factorize repo settings

-rename isSource() to isValidSource() and rewrote content
- tested with latest backp's git-mirror tool v0.14.1
- documentation tip with SSH keypair

using **kwargs instead

cache storage only store the current group