Add ability to pause and serialise state of emulator to disk

[djhworld]

Just like a virtual machines, it would be nice to have the ability to serialise the state of the emulator to disk and reload it into the emulator (even one on a different machine!) and resume playing from where you left off

Would have to take into consideration stuff like

• Graphics -> how can we serialize the state of the graphics driver? In particular the state of the OpenGL window
• Sound -> When implemented