Materialized view `node_path`: Delete functions.
minor
Materialized view `node_path`: Introduced `npt_cancel` and tested a full (delete,) insert, cancel, update & delete cycle. The update seems to be *very* slow and need to be fixed!
minor
Removed slow `npt_update` functions
Automated function generation/destruction upon `init/drop-db` plus `node_path` view materialization upon session setup