Add very basic support for Raptor
Add support for Vinyl Goddess From Mars
Map editor: Change texture map repeat flag to minimise visual artefacts
Map editor: Only draw grid if size is > 1x1
Map editor: Load .png images as map indicators, and do so for 'unknown tile'
Map editor: Show alternate indications if supplied by libgamemaps
Map editor: Add support for indicator characters 0-9,A-F
VGFM: Add .scr files to XML
VGFM: Add .gra files to XML