remove [r0] dest, make proper branch instruction with link, add branch logic to assembler

-TODO: update rtl to match
asm: handle symbol reference fixups
asm: add argument parsing and hex file outputting
replace test.hex with test.asm now that we have an assembler
.gitignore: add *.hex back
collapse long form branch into short using nv conditional

add asm support
add cpu support
cpu: add branch delay state to more properly handle killing the next instruction