Disassembler: Made it not raise an exception when an invalid instruction is disassembled, because that seems pretty normal and should not be an error.
MplabInstruction: Freeze the opcode string so it cannot be modified by accident.
Renamed the 'addition' example firmware to 'Addition' to match the others, which are all capitalized.
mplab_instruction_spec.rb: Removed a TODO that was already accomplished.
Added and removed some TODOs.
Updated RPicSim to support MPLAB X v2.05.  The only noticeable change from v2.00 is that the 'inc' field of MplabInstruction is now in the same units as code space addresses, which is a good change.
MplabInstruction: Got rid of the #inc method because it is not very useful.