Change bools to bool32 (guaranteed size)
Add drawcall flags for clearcolour/cleardepth
Add D3D11 driver side call to fetch drawcall by event ID
Allow specifying a background colour per-column on a TreeListNode
Further progress on pixel history view

* Added simple UI
* Don't apply SRGB curve to alpha data
* Account for clear calls not returning occlusion query results, and for
  depth/colour clears.
* Fix typo (shaderDiscared)