Refactored tests a bit so that they can reuse base class for DummyEndpoint.
Added basic method to forward a backout request to partner.
Added path for endpoint-to-endpoint commits.
Had been putting parameters for WaldoNumVariable's initializers in backwards.
Before this commit, had not really tested endpoint calls.  This commit
tests to ensure that for endpoint calls, changes for external data are
reflected after commits.  Similarly, ensures that endpoint calls get
rolled back when they conflict with other commits.