Cache disassembled version of program

[mortbopet]

This commit adds caching of the disassembling of the current program to the Program class. This can then be used in models which rely on some form of mapping between the notions of "disassembled program line #", "disassembled instruction address" and "diassembled instruction string".

[mortbopet]

@lcgamboa this moves the m_indexToAddress calculation to the disassembled result, which can then be used, as shown, in the instruction model, but should equally be useful to rewrite the objdump method, so that that method doesn't do disassembly, but simply "adds more text" onto the already disassembled program.

[lcgamboa]

With these modifications the instruction viewer is no longer updating correctly. I couldn't find the cause of the problem.

[mortbopet]

thank you for that; i was using the instruction PC for the row; should have done as in 03a31f6