Update build structure to ensure stability and manageability

[TobyHFerguson]

I think I should be much more prescriptive in the build to make it easier for people to use.

In particular I should fix the exact versions of CDH and other parcels, and then tag these releases. That way one can check out a specific tag and know that it worked with that specific release of CDH, CDSW, Anaconda, Spark etc. etc.