Code cleanup and documentation

[sameer-s]

• [x] Remove unnecessary debug statements
• [x] Establish the proper interface for the Simulator class
• [x] Enable a headless mode (fully decouple Simulator from Display)
• [x] Add more configuration options:
  • [x] MEM_SIZE (to a max of 1<<32)
  • [x] ~IO_SPACE_ADDR (split into min and max)~
  • [x] ~Locations of specific MMIO devices~
  • [x] PAGE_SIZE (be sure to document what this means exactly - this refers to the granularity at which the simulator allocates memory, and has nothing to do with any virtual memory mechanisms (which do not exist on the LC-3.2)
• [ ] Establish documentation

[sameer-s]

Good for now. More thorough documentation to come when the project is more mature.