Some way to keep or retrieve evaluation strings

[martinmcclure]

Under some circumstances, it would be nice to be able to keep the contents of evaluator sub-panes, or to retrieve the contents of recently closed ones.

For instance, this sequence is fairly common:

• Evaluate expression 1 in an inspector pane, resulting in object A.
• Evaluate a expression 2 in the inspector pane for object A.
• Edit expression 1 to form expression 1a, and evaluate that, resulting in object B.
• Evaluate expression 2 in the inspector pane for object B.

This is currently awkward, because evaluating expression 1a replaces the inspector pane for A with that for B, closing any evaluators you had in that pane. Might be nice to keep them by default?

The fix for #111 would help in slightly different cases, especially when inspecting temporary variables in a debugger frame, and stepping.

Having a viewable history of recently-used evaluations would also be good, as well as a way to save a library of commonly-used expressions.

[rjsargent]

a "do it" log file. external, so one can't lose them accidentally.