DocBuilder fixes

- Moved SortItems to astExpressionDocBuilder
- Split out queryShuffleDocBuilder
- Introduced queryHorizonDocBuilder
- Renamed catchNotImplemented to catchErrors and made it print exceptions nicely
- Moved non-perty test classes to Cypher internal
- Fixed ToStringDocBuilder to correctly handle nulls
Ensure solved pattern predicates are added to the left query graph tail

o Fixes a bug where pattern predicates where added post-aggregation
  (to the aggregating QG)
Merge pull request #2599 from systay/pattern-expression-bug

Pattern expression bug