Improved processor emulator

[cardillan]

A new processor emulator should provide these features:

• Any valid mlog in text form can be used as input, not just Mindcode-specific compiler output
• Support for all existing versions/targets (6, 7, BE)
• Matching Mindustry processors behavior of the given version exactly
  • Matching token recognition and literal evaluation
  • Identical instruction execution (where implemented)
• Tick-based emulation, including accumulator, delta time.
• Full-speed or (optionally) real-time emulation, correct execution of waits in both cases
• setrate support
• Emulating at given FPS and overdrive
• Execution limit specified either in ticks or in instructions executed
• Capturing the processor's output (the contents of the text buffer).

The ultimate goal is to be able to use the processor emulator for emulating parallel-processing or subframe processing on schematics. The processor must therefore respond to tick events, which will be generated outside the processor.