use sprites to draw cursor and board

this is a bit more code, but ten times less cycles to
draw the board and the cursor. the latter now looks slightly different,
this is somewhat unintentional, but only slightly.

also board is now drawn at the background layer, while
everything else is on foreground. doesn't matter much, but
makes more sense.

in uxn32 redrawing the cursor erases figures. looks awful and is a bug.
but this happens probably because uxn32 lacks the recent update to
a screen device.

refactoring and optimization

- remove logic from drawing code (also simplify)
- remove ability to make move with space key
- fix bug where game instantly restarts at the end
(key release event was triggering the restart)

compact board drawing code

also make cursor change color in place

gitignore: ignore sym files and snarf

remove makefile and update readme

major refactoring

- fix bug when game restarts and board doesn't get cleared
- optimize by using immediate opcodes and fallthrough subroutines
- lint with uxnlin
- format with uxnfor
- store x and y coordinates of the cursor in different bytes
(i thought this was a cool memory hack, but since the variables
are located in zero page this doesn't save memory, on the contrary,
it adds unnecessary complexity to manage packing and unpacking
coordinates from nibbles)
- remove loops from check-win
- remove nested comments
- avoid redoing some work when game restarts (restart code
now jumps to code that is necessary to only reset game state and
clear the board)

readme: correct prerequisites

apply optimizations

add lint to makefile

makefile: allow uxnasm to be used as an assembler

init