Setting the cache size to 0 bypasses the cache completely.
This is necessary during development to ensure newly-changed code actually gets run.
Also fixes the error pane in the params gui.
* make params warning pane large enough to see contents
* rename sizers in preferences dialog descriptive names
* add shapely version bound
* add option to disable stitch plan cache
* remove out-of-date wxg file
* make a cache size of 0 disable the cache
You can't have a module and a package named the same thing. PyInstaller wants
to import the main script as if it were a module, and this doesn't work unless
there's no directory of the same name with a __init__.py in it.