Restructure GUI subdirectories to reduce cyclic dependencies
- GUI/Models now has subdirectories
- Item related files moved from GUI/Models to GUI/Items
- Some directories moved directly under GUI/
- GUI/Views/Toplevel collects files that were directly under GUI/Views/
- GUI/main moved to App (out of GUI)
- removed numerous two-way includes
- corrected a few relative include paths
Edited by Wuttke, Joachim