Fixed a bug in ExecuteResponseBuilder, added more tests, cleaned up.

*Fixed a bug in ExecuteResponseBuilder, added some tests for the class
*Removed some warnings
*Reduced size of the tif images used for integration testing and accordingly also reduced the waiting time for asynch execute requests. 
*Now an exception is thrown, if something goes wrong while storing a result. Before that you just got an ExecuteResponse saying "Process succeeded" but with an empty ProcessResult-element.
*Removed duplicate XmlSchema-1.1 dependency, now only XmlSchema-1.4.2 is used. 
*Enabled three ignored Execute tests.