Add endpoint for getting provisioner queue metrics.
add docs for queue metric API.
Enforcing max cluster and max node settings within a tenant.
Trying to create a cluster that violates the max will cause the
request to fail with a 409. Similarly, trying to lower the max
below whats already in use will cause the request to fail with a
409.
Merge remote-tracking branch 'origin/develop' into feature/queue-statistics
Merge remote-tracking branch 'origin/develop' into feature/tenant-quotas
Merge remote-tracking branch 'origin/develop' into feature/queue-statistics
cache the queue metrics and make sure tenant names are used
instead of ids, and update docs and changelog.
Merge remote-tracking branch 'origin/develop' into feature/queue-statistics

Conflicts:
	CHANGELOG.md
	docs/docs/source/rest/rest-links.rst
checkstyle fixes.
fix doc typo and fix lock namespace.
Merge pull request #301 from continuuity/feature/queue-statistics

Feature/queue statistics
Merge remote-tracking branch 'origin/develop' into feature/tenant-quotas

Conflicts:
	CHANGELOG.md
	server/src/main/java/com/continuuity/loom/admin/Tenant.java
	server/src/main/java/com/continuuity/loom/provisioner/TenantProvisionerService.java
	server/src/test/java/com/continuuity/loom/provisioner/TenantProvisionerServiceTest.java
Merge pull request #302 from continuuity/feature/tenant-quotas

Enforcing max cluster and max node settings within a tenant.
Refactor lock logic into a common class.
Merge pull request #324 from continuuity/feature/refactor-locks

Refactor lock logic into a common class.
Merge remote-tracking branch 'origin/develop' into feature/mongodb

Conflicts:
	CHANGELOG.md