Add EntityMappings of higher arities

Bump version to 0.1.12
test: Make the Lookup an Option rather than "phony" -1
Move version to version.sbt, bump to 0.1.13-SNAPSHOT
Add 'NotSet' to Lookup ADT, move into Lookup object

Removes need for Option[Lookup]
Bump version to 0.1.13
Merge branch 'dev'

* dev:
  Bump version to 0.1.13
  Add 'NotSet' to Lookup ADT, move into Lookup object
  Move version to version.sbt, bump to 0.1.13-SNAPSHOT