add provisioning method and extensibility to SCM service

Change-Id: I2c962c5806abfa5f85ecbc129c48c3c1b2004ed0
Reviewed-on: https://q.tasktop.com/alm/s/c2c-oss/gerrit/85
Tested-by: Hudson
Reviewed-by: Myles Feichtinger <myles.feichtinger@tasktop.com>
Tested-by: Myles Feichtinger <myles.feichtinger@tasktop.com>