- 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.
- Removed usage of per-vertex ClipRect.
- Replaced usage of GSlateScissorRect with new FSlateWindowElementList::PushClip/PopClip functions.
- Defined WITH_OBSOLETE_CLIPPING_API to switch to old implementation for older engine versions.
- Added ImGui Module Manager that that implements module logic and manages other module resources.
- Added Texture Manager to manage texture resources and maps them to index that can be passed to ImGui context.
- Added Context Proxy that represents and manages a single ImGui context.
- Added Slate ImGui Widget to render ImGui output.