Improve `fre cmor run` functionality

[ilaflott]

generally, error handling, directory targets and data movement could all be a touch clearer. I didn't get to clean that up as much as i wanted to with PR172 .

additionally, too many print statements. some extra bare-bones doc should really help. the markdown README in the cmor directory isn't right either...

lines like the following add duplicate date-times into the array- to be avoided!

     iso_datetime_arr = []
     for filename in var_filenames:
         iso_datetime_arr.append(
             filename.split(".")[1] )

also some globbing problems- a lot of files are targeted even when the var list is small. if i were a crazy person (and i occasionally approach such a mood), i'd say it was actually booting each individual file into memory, before it realizes "not relevant" --> lets make sure that doesn't happen.

I may edit this with more desires as i go along...