App-level monitoring

Rationale
The staggering backlog of the job queue on the English Wikipedia shortly after the deployment of MediaWiki 1.17 showed the need for system health monitoring of application-level, MediaWiki-specific parameters.

Additional documents

 * User requirements:
 * Specifications:
 * Software design document:
 * Test plan:
 * Documentation plan:
 * User interface design docs:
 * Schedule:
 * Task management:
 * Release management plan:
 * Communications plan:
 * Status updates