Set the default filename when calling getSaveFileName() in PNGBuildingDialog.
Removed empty () from tooltips for tools without a keyboard shortcut.
Experiment with converting smaller areas of BMP images to 32bpp to save memory.

BMPToTMX::loadImage() used to convert the whole image to 32bpp because that
is the fastest format for getting/setting pixels.  However, the large size of
images (6000x6000 for example) results in hundreds of MB of memory being used.
The devs images are 8bpp .bmp images.
Fixed bogus error message in TemplatesFile.
BuildingEd: allow "none" floor tiles.
Ported MapNoBlend stuff from TileZed.