- Removed explicit PCH.
- Fixed includes to compile for all supported engine versions, including non-unity builds.
- Configured build.cs to treat ImGui as an engine module and added stricter compilation rules.
- Added SImGuiLayout to resets layout and house SImGuiWidget.
- Module manager creates SImGuiLayout instead of SImGuiWidget (eventually it should be replaced with a higher level object, like AHUD).
- Reworked ImGui canvas dragging and scaling and moved to SImGuiCanvasControl.
- Removed dependency on ImGui internal cursor data. New presentation is cleaner and doesn't use cursor data.
- Rendering code could be simplified after layout reset provided by SImGuiLayout.
- SImGuiWidget still handles input, rendering of ImGui draw data and activation of SImGuiCanvasControl.
- All widgets are in own subfolder.
