Create integrity checker tool

[demiankatz]

It would be useful to have a tool (web-based, CLI, or possibly both) to check for integrity problems in the system. Some example checks:

• Missing required datastreams in active objects
• Objects in inappropriate locations for their state (e.g. deleted outside of trash, active in holding area, etc.)
• Missing auto-generated datastreams (MASTER-MD, OCR-DIRTY, etc.)

A web-based tool would be useful for quick human-initiated checks. A CLI tool would be useful for automated checks (e.g. to allow a system like Nagios to trigger an alert if something is out of the ordinary).