Added additional properties to TripHeader for use in TubsWeb.
NHibernate join didn't work as expected, so changed to use a reference instead.
...and one last time.  WebApi serialization doesn't like the NHibernate lazy-load proxy.

Vessel is pretty small, so it's no big deal to eagerly load the entity.
Added "ClosedDate" to TripHeader.

Added missing "sealed" modifier to a number of entity mappings.
Added TripHeader search capability.
Added .ToString() method to TripHeader.