Add single-resource shared SVG renderer.

Add single-resource shared SVG renderer.

Instead of using multiple SVG files to render the in-game chess pieces the
renderer now uses single SVG file containg all pieces.

Any SVG file can be used but it must contain the required elements.

For white:

	wpawn, wrook, wknight, wbishop, wqueen, wking

And for black:

	bpawn, brook, bknight, bbishop, bqueen, bking

By default, an embedded SVG file is used.