New commands have been added to the assembler
Code Rearrangement

- Moved some code into sub folders
Added support for DB (DataByte) and DW (DataWord) commands to initialize memory with data
Assembler, Emulator enhancements
- Assembler produces a memory image
- Assembler now generates the correct opcode values
- Emulator is initialized now by a memory image
Corrected the initialization
Merge branch 'master' of https://github.com/pld-lessons/simple_soc