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.

Test Plan:

• verified that non-owner cannot see the details of the audit and cannot modify

it

• verified that all the audit reasons can be detected
• tested dropdown filtering and package search
• verified really normal change not detected
• verified accept/concern a commit
• tested enable/disable a package for auditing
• verified one audit applies to all <commit, packages> to the packages the

auditor owns

• verified that re-parsing a commit won't have effect if there exists a relationship for <commit, package> already

Reviewers: epriestley, nh

Reviewed By: epriestley

CC: aran, benmathews, btrahan, mpodobnik, prithvi, TomL, epriestley

Differential Revision: 1242