fix issue#695: Refactor FormulaEditor ExternInternRepresentationMapping

fix lint warning in ExternInternRepresentationMapping
refector FormularEditor

#725 

https://jenkins.catrob.at/job/Catroid-Multi-Job-Custom-Branch/603/
org.catrobat.catroid.uitest.content.brick.IfBrickTest.testIfBrickParts is unsbale in the master too -> #725