Reduced palette

You guys should know what this is by now. If you don't, you really need to catch up. =P

We should check with toaster and others involved to check this thing is actually ready to go though, the number of changes to the palette itself over the last year has been absurd.

See also http://git.magicalgirl.moe/STJr/SRB2Internal/issues/8

See merge request !13