When converting predicates to filters, symmetric comparison predicates can now compare a value to a key in addition to the usual key-to-value order. Added error checking for unhandled combinations like key-to-key. Fixed a crash converting a CONTAINS predicate into a filter. Added support for constant value expressions inside aggregate expressions. Allow sets as aggregate expressions just like arrays, except in BETWEEN predicates where order matters. Flatten NOT predicates into more specialized filters.
When converting filters to predicates, use constant value expressions inside aggregate expressions. Convert to a BETWEEN predicate when possible.
Replaced predicate round-tripping integration tests with systematic unit tests for converting in either direction, plus unit tests for round-tripping and symmetry.
Refined exception names and messages. Realphabetized files in groups.
