* [FORMAL_LANGUAGE,NEW] New module supporting the formulation of formal languages. Currently contains:
  * algebraic_signature/1
  * relational_signature/1
  * signature/1
  * atomic_formula/1
  * formula/1
  * individual_constant/2
  * predicate/[2,3]
  * term/1
* [SET_THEORY,NEW] Added arbitrary_[intersection,union]/2 wrappers.