Make save and load statespace commands available in ProB2-UI

[leuschel]

In Tcl/Tk and probcli it is possible to save and re-load the state space.
It would be nice to have this feature also in ProB2-UI.

[iTitus]

What is the semantic of such an operation?
How does it differ from just reloading the machine?

[leuschel]

After reloading the state space is empty (except for the root state) and all states and transitions need to be re-computed which can be expensive.