Summary
- amending 689997a8a582
- subsection is always %important
- no need for %unimportant for proofs of proposition
- redo tagging-related changes from a06b204527e6, 0f4d4a13dc16, and a8faf6f15da7
- revert to 56acd449da41
- merge
- more tagging
- updated tagging for 9 theories: Cross3, Determinants, Tagged_Division, Change_of_Vars, Extended_Real_Limits, Fashoda, Finite_Cartesian_Product, Function_Topology, Finite_Product_Measure
- chapters for analysis manual