Created a "plot display window" which is essentially recordsweep window without the instrument setup part.
Also modified G2Gui accordingly, and started code to allow the mainwindow to figure out which plot window was most recently active (so that the main menu and toolbars
can eventually be shared instead of being copied for each plot).
Merge branch 'sliders' of https://github.com/gervaislab/g2python into sliders

Conflicts:
	recordsweep/G2Gui.py