Add StaticValidator warning when a rule references a missing name.
Merge pull request #59 from ggp-org/static-validator

Add StaticValidator warning when a rule references a missing name.
Rename the "PropNetFactory" to "LegacyPropNetFactory", and add a comment
saying that using OPNF is preferred.
Switch to using OPNF instead of the legacy PNF in the
SamplePropNetStateMachine.
Merge remote-tracking branch 'upstream/master'