Added "BMP To Layers" tool.

This tool puts the BMP-generated tiles into the map and erases the BMP to
black.
Fixed BmpAlias tilenames not being normalized when used by BmpBlender.
Fixed StampBrush/BmpBrushTool/BmpEraserTool not updating the brushItem() correctly.

The last point returned by calculateLine() doesn't necessarily match the
end coordinate passed to it.  Observable when painting from right to left or
south to north.
Fixed another GCC-better-than-MSVC issue.
Removed BmpToLayers affecting tiles outside the painted area.

I thought this was needed but the actual problem was with non-normalized
tile names.
Fixed BmpToLayers not working in Release build.

I had Q_ASSERT around some needed statements.  Never do this again.
Improvements to the BmpToolDialog.

- Added "Warnings" tab that displays missing tilesets, missing layers, and
  undefined aliases.  Moved the HELP button here.
- Added buttons to clear all rules and blends from the map.
- Disabled export buttons since they're not implemented.