Fix for the NullpointerException upon copying a copied brick
fixes #674: Copying objects with local variables

 * fixed the double variable issue
 * fixed some reference issues regarding the ```ChangeVariableBrick```
   and ```SetVariableBrick```

**Jenkins testrun:**
https://jenkins.catrob.at/job/Catroid-Multi-Job-Custom-Branch/374/
Unified the names of copied sounds and looks.
Removed duplicate of copySound() method.
Added description for copied sound in strings.xml .
Fixes #679

Added unregisterReceiver method
Merge pull request #682 from Catrobat/nameOfCopiedObject

Unified the names of copied sounds and looks.
Merge pull request #683 from Catrobat/issue#679

Fixes #679
Merge pull request #655 from Catrobat/CopyACopiedBrickCrashesApp

Copy a copied brick crashes app
Merge pull request #678 from Catrobat/issue#674

fixes #674: Copying objects with local variables
Fix issue #660

Activate "Don't keep activities" in Developer options to reproduce this bug. When invoking the FormulaEditorFragment from the ScriptFragment it becomes registered with the ScriptActivity as the ScriptActivity is a FragmentActivity. Hence, when leaving the ScriptActivity by entering the stage and returning again by leaving the stage, it will try to resume its fragments. During this process it tries to access formulaTextFieldId of Formula.java. However this field is not available (= null) because it is declared transient. When not declaring the formulaTextFieldId as transient the NullPointerException will be avoided though the FormulaEditorFragment will be loaded anyway. Because all of this only happens when leaving the ScriptActivity via the PlayButton the FormulaEditorFragment is removed beforehand. So if now returning from stage the FormulaEditorFragment is not registered with the ScriptActivity and will not be started by the ScriptActivity.
Fix testReturnFromStageAfterInvokingFormulaEditor

Run testcase testReturnFromStageAfterInvokingFormulaEditor only when 'Don't keep activities' is set.
fixes LookFragmentTest#testCopyActionMode

Two strings were merged together but missed in some UiTests.
Merge pull request #687 from Catrobat/fixTestCopyActionMode

fixes LookFragmentTest#testCopyActionMode
Merge pull request #680 from Catrobat/CatroidCrashesAfterReturningFromStage

Fix issue #660
Merge branch 'master' into SOR-facedetection
minor clean-up