Implement `AIM` instruction

[craigthomas]

Add the AIM instruction. Performs a logical AND of an 8-bit immediate value with the contents of a memory byte and stores it in the designated memory byte. Meant to collapse the LDA, ANDA, and STA 6809 operations to perform the same task.

AIM:
Direct - $02, 3 bytes
Indexed - $62, 3+ bytes
Extended - $72, 4 bytes

The command works with the following syntax:

AIM #$0E;$FFFE

Note the semi-colon used to separate the immediate value and the memory address.