KiPadCheck works with nightly, seeking feedback

Updated KiPadCheck GUI to use a separate file generated from wxformbuilder.
Please let me know how this affects running on MacOS and Linux. Better?

THIS IS FOR NIGHTLY ONLY, NOT 4.0.6 STABLE.

The distribution is now two files kipadcheck.py and kipadcheck_gui.py. Both must be placed in the plugins directory.

The README.md is updated as well to be a bit more organized with ABOUT and USE closer to the top.

Feedback welcome!