Generalized met workflow

met.workflow.gen.R can be used for 
- downloading raw NARR
- converting to raw NARR to CF 
- Rechunk/Permuting for faster extraction times
- extracting for specific sites
- met2model.SIPNET (ED2 should also be working)

parameters are set in met.workflow.params.R
Have you tried the [`killdbcons()` function](https://github.com/PecanProject/pecan/blob/master/db/R/query.base.R#L81)? I wrote that function to do exactly this, but @robkooper pointed out that it is only needed if we are doing something wrong, and he therefore marked it deprecated.