Editor added

Editor added, but it's just a shell - the basic GraphicsDevice +
WinForms thing.
tweaked some stuff, added menu bar and 1v1meirl
Changes to editor; extra test files removed

Work on drawing circles with PrimitiveBatch; fixed the white cross of
doom; can now draw ginger kids to my heart's content.
More editor work

Can now draw circles filled and outlined; now working on rotatable
rectangles. Open dialogue works, but no level loading code in place.
Editor can now load and save files

Drawing rectangles now works. Can load and save .json files. Added a
function to bypass the Content Pipeline for images.
More editor work

Tileset selector added; just a shell for now
Ginger kid now has his own window

Also, layout tweaks.