tiles.rc: impl TileSpec class for reading tile specification

and rewrite MakeTiles to use the TileSpec class
tiles.rc: revise syntax of tile specification

changed my mind on tile specification syntax
tile animation: copy animation information from Java source code to tiles.dat
tiles.rc: rename tiles.dat to tiles.rc, bring TileSpec into main program
tiles.rc: add comments to delineate different categories
tile animation: animation is now controlled by tiles.rc
tile animation: cleanup, remove obsolete ANIMBIT constant
tiles: transfer ZONEBIT knowledge to tiles.rc

and synthesize ZONEBIT,ANIMBIT when saving (for compatibility)
MakeTiles: impl generation of different-sized tiles
MakeTiles: allow tiles recipe to be more size-agnostic
MakeTiles: impl support for SVG files

SVG files are converted to PNG files at the appropriate resolution
by calling out to Inkscape.exe (must be installed somewhere)
MakeTiles: when generating intermediate images, use a staging directory
MakeTiles: fix bug in SVG->PNG logic
MakeTiles: when converting an SVG file, specify DPI rather than expected width/height

This way we can handle multi-tile SVG source files (e.g. for the larger zones) correctly.
MakeTiles: allow making generated images of an SVG image in a subdirectory
tiles.rc syntax: allow inheriting of another tile's images/attributes

To inherit, just put the name of tile you want to inherit from in parenthesis
at the beginning of the specification.
E.g.

road-1-1     (road) roads/1-1 (road-north)(road-south)

will define a tile named "road-1-1", which first starts with all the images
and properties of tile "road" and then layers on top of that the 'road/1-1'
image, and then sets the 'road-north' and 'road-south' flags.
graphics: high-color water
graphics: make a high-color DIRT tile image
graphics: use a transparent layer to implement wires
graphics: experiment with new forest graphics (work in progress)