PeakFind has been added to the context menu when right clicking on a drawn
histogram.  There are still problems to overcome:  the PeakFind panel needs
to communicate back to the gui that it has been deleted (to overcome a
segmentation violation error when the pointer is deleted a second time);
multiple PeakFind menu items appear when the canvas is split into multiple
pads (even though it is not added if already in the menu???); still no way
found to get a context menu for the folder icons (Files, Online, Groups);
need to figure out a way to let the user choose the active pad, so he/she
can pick any drawn histogram for peak finding (currently it only works with
the latest drawn histogram).  Also, Clear All online histograms has been
added to the main menu (it used to be a button).