An experiment with arities
Revert "An experiment with arities"

This reverts commit 370f3f6a1ab8489ffc96629dbee944d2b9e35274.
WIP: made arities label-types (so far only one thing - many); added lift and flatten
More explicit arities
Changed to a separated arity again
- renamed Traversal to Path
- added 4 types of arity and their multiplication
- added conversion of the internat container (List for now) to one that corresponds to the out-arity
- WIP: test
WIP: updating tests
Fixed composition eval; fixed tests
Cleaning up sources; forgot to add titan impl
Merge branch 'feature/query-dsl/arities' into feature/static-queries