Adding RelatedActions and documentation

I created this feature branch to propose an alternative for
representing workflows and relationships among Actions.  I think it
only requires a single additional entity in the Core schema and removal
of the ParentActionID from the Actions table.  This is mainly because
there are relationships among Actions that are not strictly
parent/child relationships (particularly in sensor data workflows).  I
added a long article to the documentation in this feature branch
showing simple and more complex examples of how this can be used for
both samples and sensors.
Merging new stuff from the master into this FB

There was a new diagram in the Master branch and a couple of other
tweaks that I moved over into this Feature Branch in preparation to
merge it back into the Master.
Resolving merge conflicts so I can merge with master
Merge pull request #21 from UCHIC/Workflows_Alternative

Adding RelatedActions and documentation to Master after resolving merge conflicts.  This merge does the following:

1. Removes ParentActionID and relationship from the Actions entity in the Core schema
2. Adds a new entity called RelatedActions and relationships with Actions to the Core schema