LisaTest API additions for running tests from Notebooks

Created by: bjackman

This adds some stuff to the LisaTest API so that test classes can be instantiated in notebooks, the tests can then be run and the results interactively analysed to figure out the causes of test failures. An example of such a notebook will be submitted separately.

Summary of the changes:

Awkwardness to allow instantiating LisaTest objects:

• Add $LISA_HOME to $PYTHONPATH so the tests package gets discovered
• Add an empty LisaTest.runTest method so that __init__ (inherited from TestCase) can be called without the methodName parameter.
• Rename the "abstract" EasTest base class to avoid it being detected as a test class by nosetests

API additions

• A "public" LisaTest.runExperiments method to trigger running experiments
• A LisaTest.experiments attribute aliasing LisaTest.executor.experiments, for convenience.

And a fix for LisaTest.get_sched_assert which looks like it never worked.