Fix for Empty Code.xml issue#935
* New Writing Process: 1. Write to tmp_code.xml 2. Delete code.xml 3. (usually atomic) rename tmp_code.xml --> code.xml
* New SanityCheck for saveProject, loadProject
* Solved Locking issue with xstream
* Solved 3 fails in Speakbricktest + 1 test in utilstest
Merge pull request #1024 from Catrobat/issue#935

Issue#935