Implemented the first OpCode - clears the screen
OpCodeDecoder uses Memory and OpCodeFactory
OpCodeDecoder uses class MachineState to read program counter
Chip8Emulator changes PC only if it was not changed by the execution of an opcode
Implemented OpCode1NNN (jump to NNN)
implemented OpCodeFactory for the existing opcodes
Implemented rudimentary Memory class
First Chip8 program - clear screen, goto 0x200
OpCodeFactory throws an error if it does not know the given code