UI updates

[shapiromatron]

Updates from a review of BMDS Online. Changes include:

• Change h2 -> h1, and 23 -> h2
• Label complex tables using id and headers properties
• Add estimate_background as an option to nested dichotomous
• Show degrees used for each dataset in multitumor instead of "auto"
• Change default show all models to false for nested dichotomous and multitumor, consistent with dichotomous and continuous
• Fix bug in scrub_db migration command
• Remove extra API schema endpoints; was failing validation in generated openapi specification
• Remove throttle api endpoint

Release this as 24.1a6; require pybmds 24.1a6