* push down ValueType to ExprType conversion, tidy up
* determine expr output type for given input types
* revert unintended name change
* add nullable
* tidy up
* fixup
* more better
* fix signatures
* naming things is hard
* fix inspection
* javadoc
* make default implementation of Expr.getOutputType that returns null
* rename method
* more test
* add output for contains expr macro, split operation and function auto conversion