admin page

[NaevaTheCat]

Needed stuff:

• [x] fix bad selector for booking banned rooms
• [ ] bookingtypes needs a validator for oops all banned rooms
• [ ] pass messaged warning people about undefined periods of the year

[NaevaTheCat]

Admin form for setting up config should be nicer, at minimum should move models to inlinemodels for simultaneous editing. will require moving to ParentalKey see https://docs.wagtail.org/en/latest/topics/pages.html#inline-models

[NaevaTheCat]

Above is done, but it breaks validators during drafting. Need to fix

[NaevaTheCat]

I think I figured out why above was broken. Some things need saved models to work, but others just had bad tests/selectors for test cases self-selecting and determining overwrite. Fixed in 645ec3946bc00ae4cf4e1d4f12af51ecb1af15d1