Implement essential subscriptions functions

* Look for projects with monitor enabled on plugin load
* Keep track of manifest repos that has subscription enabled
* Keep track of projects defined in manifests being monitored
* Update when project.config is changed
* Update when manifest changes
* Update on project changes (for projects in manifests being monitored)
* Repo where generated manifests are stored will not be monitored

Change-Id: I63c749487f52c58d20ce8004bdb892ae4b78afd6
9 files changed