* Add Start/End subquery node skeleton
* Added a test query that triggers complex interna in the future and needs to proof that our work is side-effect free.
* Add template function to statically assert size of type
* Add Start/End subquery node skeleton
* Add Start/End subquery node creation to ExecutionNode
* Cleanup SubqueryEndNode
* Add test file
* Add isEqualTo to ExecutionNode
* Subquery nodes cleanup
* Update ExecutionNode tests
* Updates to testing code
* More updates
* Add optimizer rule
* Fix optimizer rule
* Fix optimizer rule (again)
* Add a public function to get plan from query
* Fix register planning
* Add test for splicing subquery nodes
* add static asserts for sizes of SubqueryStartNode and SubqueryEndNode
* Add comment about statically asserted size
* Fix isEqualTo virtual and override dance.
* Fix isEqualTo, remove static_assert_size
* Remove a TODO; the plan owns the ExecutionNodes
* Only add stealPlan to Query when testing
* Remove another static_assert_size
* Disabled subquery splice rule by default
* temporarily modified test
* Fixed windows compile
* Fixed unused variable warning
* reduce extractions to projections
* recycle string buffers in SocketTask
* micro optimizations for mmfiles indexes
* added special lookup function for _key
* moved function into the correct file
* speed up key buffer allocations a bit
* added noexcept specifier
* correctly name variable
* explicitly move bounds
* fix and speedup from/toPersistent functions
* reuse string from ManagedDocumentResult for multiple lookups
* use move-assign
* a bit less work for single server
* speedup AQL function HASH
* single fetch optimization
* performance optimization for the case when no documents need to be returned
* make reduce-extraction-to-projection a RocksDB-only optimizer rule
* cppcheck
* try to fix compile error on MacOS
* bug fix for MacOSX
* missing namespace (in Windows compile)
* reduce extractions to projections
* recycle string buffers in SocketTask
* micro optimizations for mmfiles indexes
* added special lookup function for _key
* moved function into the correct file
* speed up key buffer allocations a bit
* added noexcept specifier
* correctly name variable
* explicitly move bounds
* fix and speedup from/toPersistent functions
* reuse string from ManagedDocumentResult for multiple lookups
* use move-assign
* a bit less work for single server
* speedup AQL function HASH
* single fetch optimization
* performance optimization for the case when no documents need to be returned
* make reduce-extraction-to-projection a RocksDB-only optimizer rule