1.12.0

API BREAKING:
* Remove NimrodEntity
* Remove Experiment#getToken()
* Replace AgentInfo#{getPath,getAgentPath}() with a version
  return java.nio.path.Path

API:
* Make MachinePair fields final

Agent BREAKING:
* Remove NIMROD_JOBPATH environment variable

Database/Postgres:
* Remove internal "path" fields
* Schema version bump to 5.0.0
* Fix a bug in the 2.1.0 -> 3.0.0 migration script

Database/SQLite:
* Remove internal "path" fields
* Schema version bump to 4.0.0