Fixed a postscript font scaling issue, finally!

You might think that setting a font's size will rescale the font to
the desired height, but this is not true. You get a vertically
stretched (or squished) font that way. You want to set the height,
which properly rescales everything. This commit fixes that.
Enahnced properties dialog, added auto-scaling buttons
Disable mouse manipulation when properties dialog is open
Use named keys for property window

I am thinking about how to add axis scaling radio buttons, and that
will require interaction between the radio buttons and the min/max
values. As such, I have moved lexical variables into hash keys or
named components of the group box.
Take axis' opinion of numerical validity into account in preferences dialog
Switch back to lexical is_auto in preferences dialog

I realized that the best way to pay attention to handle knowledge
of automatic scaling and other axis properties is to add event
listeners that update the various widgets and update lexical
variables that cary the current state.
Switched the properties dialog to use event listeners.

I also decided to allow the properties dialog to live alongside
the plot object, which required some coordination of destruction
events to ensure proper cleanup.
Remove extraneous print statement
Revise old notifications for mouse movement