Theorem continuous_add'

refactor(analysis/topology/topological_structures): use to_additive to derive topological_add_monoid and topological_add_group

feat(analysis/topology): add tendsto and continuity rules for big operators

Merge branch 'master' of https://github.com/leanprover/mathlib

refactor(data/finset): fix formatting issues

feat(topology): add topological structures for groups, ring, and linear orders; add instances for rat and real