Fix typo, getSematicProperties -> getSemanticProperties
Add SemanticPropertiesTranslationTest for Scala API

Fix join operator to user proper EquiJoin constructor so that semantic
properties are actually retrieved.
Add Scala API completeness Test

This is very naive right now, just checks whether a function of the same
name is available. There are lists and regex patterns of excluded
functions since not all functions in the Java API need to be available
in the Scala API.