Updated tests in maven branch

Hi @evren, I've updated the test cases in the maven branch of pellet. In essence the changes to the test classes from @ansell are reverted and the maven surefire plugin is configured to set the correct working directory as expected by the test cases. That means there is no need any longer to copy resources from classpath to file locations as discussed in https://github.com/clarkparsia/pellet/pull/3 and the test classes can also be reused as is. I also removed the StableTests and UnstableTests categories as well as the test profiles in the parent pom. Note that the test cases still need some review:

* reasoning of MechanicalEngineering.owl seems to be stuck at least in Jena (as already pointed out by @ansell) so I put an ignore annotation on it
* JenaExplanationTest is failing 
* there are warnings in TestSuite because org.mindswap.pellet.test.WebOntTestCase and com.clarkparsia.pellet.test.query.SparqlDawgTestCase don't have a public constructor

Would be nice if we can sort out the remaining issues (test cases and assembly configuration) so the maven migration can be finished soon.