Created a QueueGroup that manages per-tenant queues of different
types, such as per tenant solver queues, per tenant task queues,
etc.  Also did some cleanup around unused code that would timeout
elements in queues. It is no longer scalable to use a thread for
each queue for cleanup purposes.
small cleanup removing warnings.
Merge remote-tracking branch 'origin/develop' into feature/tenant-queues

Conflicts:
	server/src/main/java/com/continuuity/loom/guice/LoomModules.java
	server/src/main/java/com/continuuity/loom/runtime/LoomServerMain.java
	server/src/main/java/com/continuuity/loom/scheduler/CallbackScheduler.java
	server/src/main/java/com/continuuity/loom/scheduler/ClusterCleanup.java
	server/src/test/java/com/continuuity/loom/BaseTest.java
	server/src/test/java/com/continuuity/loom/http/LoomClusterHandlerTest.java
	server/src/test/java/com/continuuity/loom/http/LoomServiceTestBase.java
	server/src/test/java/com/continuuity/loom/scheduler/ClusterCleanupTest.java
	server/src/test/java/com/continuuity/loom/scheduler/SchedulerTest.java
	server/src/test/java/com/continuuity/loom/scheduler/SolverSchedulerTest.java
adding javadocs and comments on new queue group classes.
Merge pull request #253 from continuuity/feature/tenant-queues

Feature/tenant queues
Merge remote-tracking branch 'origin/develop' into feature/provisioner-apis

Conflicts:
	server/src/main/java/com/continuuity/loom/common/conf/Constants.java
	server/src/main/java/com/continuuity/loom/common/queue/guice/QueueModule.java
	server/src/main/java/com/continuuity/loom/scheduler/JobScheduler.java
	server/src/main/java/com/continuuity/loom/scheduler/task/ClusterService.java
	server/src/test/java/com/continuuity/loom/BaseTest.java
	server/src/test/java/com/continuuity/loom/http/LoomServiceTestBase.java