Merged 4 commits fixing build errors when compiling this as an engine plugin:
- Changed include directives to use full paths (ex. <ICursor.h> -> <GenericPlatform/ICursor.h>).
- Added categories to FImGuiKeyInfo properties (required for all blueprint exposed types in engine plugins).
- Added explicit configuration of PCHUsage (without that it is assumed to be UseExplicitOrSharedPCHs in engine plugins and UseSharedPCHs in game ones) - amended to work also in the older engine versions.
- Updated InputNavigation CVar to support 1: keyboard navigation, 2: gamepad navigation and 3: keyboard + gamepad navigation simultaneously.
- Added ImGui interoperability utilities mapping gamepad input events to values in ImGui navigation inputs array.
- Added to ImGui Input State support for gamepad navigation inputs.
- Refactored ImGui Input State to keep consistent interface for keyboard, mouse and gamepad updates.
Using ImGui to draw cursor helps to reduce visual error between mouse cursor and position in ImGui. But it has been reported that this works really bad when frame-rate drops and becomes unusable below ~20 FPS. Taking that into account hardware cursor seems like a better default option. Old behaviour can be enabled with ImGui.DrawMouseCursor console variable.
- Added ImGui Input State to collect and store input updates.
- Changed Slate ImGui Widget to handle Slate input events and store them in input state.
- Changed ImGui Context Proxy to copy input state to its context.
- 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.
