ROM: Galerkin verify API

[fnrizzi]

need to verify the doc API is in sync with code

• [x] steady

  • [x] syntax
  • [x] parameters
  • [x] constraints
  • [x] preconditions
  • [x] return value
  • [x] postconditions

• [x] unsteady

  • [x] syntax
  • [x] parameters
  • [x] constraints
  • [x] preconditions
  • [x] return value
  • [x] postconditions