R1:c80d1480d5aa

Add Basic Auditing Functionalities

Summary:
add basic auditing functionalities. For the related commits for a
package, we detect the following conditions which might be suspicious to the
owners of the package:

* no revision specified
* revision not found
* author not match
* reviewedby not match
* owners not involved
* commit author not recognized

The owners of the package can change the status of the audit entries by
accepting it or specify concern.

The owner can turn on/off the auditing for a package.