AMIDST PANDEL-3: Add PandelValidator

* tests: PandelValidator OK as Draft4Validator v (few rules extended
yet)
* docs: Readme and faq edits.
* Licenses: Add MIT and Apache licenses for jsonschema tests and
(planned) prefix tree.
TESTS and doctests FAIL!
AMIDST PANDEL-3b: PandelValidator tests run OK with pandas

* Need tests for NAN and corner cases.
TESTS and doctests FAIL!
ATTEMPT PANDEL-3c: PandelValidator FOR LATEST jsonschema (not inhouse
modified)

* build: Del unused sphinx-napolean setup-requiement.