RW-578: Added initial RBroker Framework unit tests.

Initial set of 34 unit tests for framework added:

- DiscreteTaskBrokerTest * 11
- PooledTaskBrokerTest * 13
- BackgroundTaskBrokerTest * 10

Note, the DiscreteTaskBrokerTest.testEndpointBadAddress fails pending a patch for:

RW-579: DiscreteTaskBroker does not detect invalid DeployR endpoint on initialization.