Adds an association between parent and derived data products

 - New Association hasParentDataProduct
 - Adds support for linking data products correctly

These changes stem from the case where the ION system is launched and several
data produts are created by the preload system but they are not activated,
when creating derived data products a dataset was required to exist for
the proper associations and links to align so that they shared the same data with
their parents.  What we really want to be able to do is have them be able to present
the parents data when the parent has data to present.
Adds visibility attribute for parameter contexts
Merge pull request #386 from lukecampbell/dp-work

Adds an association between parent and derived data products