* multi-value check resul

* Fix cycle handling in permission checks

* Search subjects with permissions

* Rename `check` package to `graph`

* Simplify graph test harness

* Add v3.LoadFile function to load a model from a file

* Test inverted model for object search

* Search objects using inverted model

* Invert intersections and negation permissions

* Fix relation inversion

* Use special characters as separators

* Separate intermediate types from subjects

* Foundation for handilng subject relations