fix analysis issue (Value stored to 'url' is never read)
Merge pull request #240 from Catrobat/analysis_issue

fix analysis issue (Value stored to 'url' is never read)
license header fix
use instancetype in sharedInstance-methods
fix when moving files if src and destination equals
always return valid path for preview image
fixes #221
Merge branch 'master' of gh:Catrobat/Catty into issue#221_2

* 'master' of gh:Catrobat/Catty:
  fix analysis issue (Value stored to 'url' is never read)
  animation improvement
  refactoring
  small improvement
  session improved with Image
  session try
Merge branch 'issue#221' of gh:Catrobat/Catty into issue#221_2

* 'issue#221' of gh:Catrobat/Catty:
  license header fix
fixes #235
Merge pull request #241 from Catrobat/issue#221

Issue#221
Merge pull request #242 from Catrobat/issue#235

fixes #235
fixes #244, weak objects (except for SpriteObjects) are temporarly stored until they are needed
refactoring
could fix #67
Merge pull request #245 from Catrobat/parser-fix

fixes #244
Merge pull request #246 from Catrobat/memory

could fix #67
fixes #250 + code optimization and cleaning
added some tests
fixes #248