Fixed [png >> shp] conversion.
ListBoxes now clear when their parent form is closed.
libshp.Commands.ConvertSpriteToPng is return
	type string now.

Added filters to FileDialogs.
Added /TestFiles dir along with
	e1.shp
	temperat.pal
Cleaned up .gitignore.
Made a string ext more platform-agnositc.
Added an About menubar item.