merging current state of developer back into master

This is a number of mission critical changes, the largest of which are:

1) totally revised dataset classes creates variables on objects for each dataframe and computes dependencies, etc.  semcog and bayarea have both been converted to this style of dataset.

2) New developer and feasibility functionality.  The proforma is documented and a draft of feasibility and developer have been written.  

Generally this build is not complete in terms of the developer model but I don't want to fall too far off master and I need to get these changes in to master to share with clients.

And this functionality needs more testing and should be considered alpha at this point.