Get Rid of "Nonsense Input"

[caitlinfanning]

1. Any illegal symbols should have an illegal symbol error
2. Check for possible label mishap (e.g. label;)
3. Off-by-one (or two?) instructions should have did you mean/invalid instruction error

[SatGarcia]

BCL now checks for typos and offers up a "Did you mean..." suggest if finding an instruction or register name that is a close match for what they actually typed in.