Create explicit opcode grouping:
- One group per row of opcodes (eg: top 3 bits).
- Put MOV and LDI into their own group.
- Put Skips into a second "Branch Unit" row.

Conflicts:
	testdata/Core1010SC_tb.v.out
	testdata/Fetch_tb.v.out
	testdata/rom.txt
Auto-generate decoding matrix, based on rows and columns of each opcode.
Make opcode group lowercase.
Initial implementation of Core1001:

- LDI.
- MOV from/to any register.
- ADD from any two registers into RA.
- LD and ST.
- BDNZ, BEQ and BNZ.

Lacks any testing, probabbly very buggy.