Re-organising CMS-HTT

[rmanzoni]

Dear @CMS-HTT/developers,

our organisation has grown up to 30 active people, great!

For a better organisation of the permissions and repositories, we created different teams along with the all in group now named Developers.

Each group has different privileges on different repositories: for instance, MC contacts can push, pull and create new branches in https://github.com/CMS-HTT/MCValidationForRun2, but, on the other hand, can contribute to other non-related repositories such as https://github.com/CMS-HTT/LeptonEfficiencies only via Pull Requests.
Developers have full access to https://github.com/CMS-HTT/2015-sync.

For now the composition of the teams is mostly common sense albeit arbitrary. Speak up if you need to be included in any of these new teams, or if you want to start a new one for a specific subject.

Cheers!