sim: cpu_sim: add decoding and prettyprinting of load/stores
sim: cpu_sim: refactor giant if-else block for decoding opcodes
sim: cpu_sim: refactor opcode handling in preparation for adding "other" ops
sim: cpu_sim: decode "other" ops; print more attributes of decoded instructions
sim: cpu_sim: decode remaining alu ops (1op regsh, long imm); this completes all ops