Parametrized and global service URL (BB-8421)

For all my projects, I add a POST service (for jenkins integration)

For the WeWantToKnow/unity3d-flash-incompabilities project:

POST http://SERVER_URL/git/notifyCommit?url=git@bitbucket.org:WeWantToKnow/unity3d-flash-incompabilities.git

I would really like the ability to:

• use a parametrized URL, so that I do have to customize the URL value for each project.
• declare this service globally so that I can enter it once for the organization