Use webhooks for branch and change detection

Bitbucket: http://confluence.atlassian.com/x/hgNODQ
Github: http://help.github.com/post-receive-hooks/

Bamboo should have a single URL where the webhooks post their data "http://tardigrade.sydney.atlassian.com:8085/bamboo/rest/latest/changes" (or similar).

1. User registers the hook on Bitbucket or Github
2. User commits and pushes to repository
3. Github/Bitbucket POSTs the change information as JSON to the Bamboo URL
4. For Plans where the repository URL matches the repository URL in the JSON data
   • Detect branches for Plan if the JSON data contains a reference to a branch Bamboo is not aware about
   • Detect changes for Plan if the Plan is using a Remote build strategy.