API Tests: Support for Nosetests parallel execution of tests

Support for nosetests parallel execution of tests.
Since all the API tests are self contained, it is not a problem to run them in parallel.
 With 8 processes running, test execution is at least 5 times faster.

Currently, the main problem with the parallel execution of tests is the reporting the results in XUnit/JUnit format, required for Jenkins integration. The standard xunit plugin does not handle multiprocessing and the beta plugin (xunitmultiprocess) has problems (the test counts are wrong).

Keep in mind that the addition of support for parallel exeuction does not change the single threaded execution of the tests.