simplify user startup file and debug window

As part of my campaign against files named like JESWhatever.py, I have
deleted JESDebugWindow.py and JESPreprocessing.py, replacing them with
jes.tools.vardebug and jes/user-startup.py respectively.

I have drastically simplified them as part of the change, removing many
definitions from user-startup and eliminating a bunch of awkward and
repetitive code from vardebug.

(Why? Honestly, I needed something simple to do that involved
destroying old code after the frustration involved in the file chooser.)