scm extension point - 1/7

SCM extension point:

1. XML CRUD
2. end-point (config, check connection, latest revision, latest revisions since, checkout)
3. DB CRUD
4. poller & agent fetch
5. view (materials UI read, build cause pop-up [pipeline dashboard, pipeline history, VSM], compare pipeline, trigger with options pop-up, stage - overview & materials, job - materials, environment dashboard, APIs)
6. materials UI - SCM pop-up (add, use)
7. SCM listing - edit, delete