* [DB_EXT,NEW] Big cleanup and partial rewrite.
  * Removing db_replace_novel/2.
  * Adding db_replace_all/2, db_replace_some/2.
  * db_replace/2 now is the only public predicate that takes a pattern.
* [GRAPH_THEORY,DOC] Improved/fixed many type and mode annotations.
* [GRAPH_THEORY,SC] Renamed edge_components/3 -> edge/3.
* [GRAPH_THEORY,SC] Removed edge_components/4. Support for typed edges will be added in a future module.
* [GRAPH_THEORY,EXT] Edge and vertes induced subgraphs now take list input (used to be ordset).
* [GRAPH_THEORY,SC] Renamed graph_components/3 -> graph/3.
* [GRAPH_THEORY,NEW] Added head/2 and tail/2.
* [SET_THEORY,FIX] subset/2 fixed.