Intermediate commit for ticket #223 and #395
Implemented ticket #430 "Renaming - Check Boxes"
Implemented ticket #441 "Renaming - Warning in case the new variable is already in use"
Implemented ticket #448 "Improve the architecture of the options dialog"
Fixed a little issue in implementation of ticket #436
Fixed an issue in implementation of ticket #6
Improved implementation of ticket #444
Fixed issue in implementation of ticket #444
Implemented ticket #439 "Editor - Collapsing"