Field: Add sampling test based on random distributions to expose overshoot
Field: Add sampling test based on random distributions to expose overshoot

This test creates a field from random numbers between 0 and 1 and assures
that sampled values are > 0. Thanks to @Jacketless for pointing out the
current bug that this demonstrates.

OceanPARCELS/parcels,OceanPARCELS/parcels