splitting out some csv parsing functions

splitting out some csv parsing functions

- reformate a Dataframe to a Series,
- create bounderies for coordinates,
- check if a unit is CF convention compliant,
- create netCDF file from a Series

See ews-epidemiology commit 922332e.

This creates input files for an epi run that are the output of an epi run from the previous day. Connects with ews-epidemiology development at the same time.

Remaining tasks to finish this work:
1) Stop loading env and depo from days before today
2) Write tests

making the Processor.py pass on non-zero exit codes when exiting - I THINK THIS COULD CAUSE PROEBLEMS WITH INTEGRATION TESTS, AS IT WILL EXIT THE PYTHON ENVIRONMENT RATHER THAN CARRYING ON TO THE ASSERTS IF THERE IS AN ERROR, WILL ROLE BACK IF THIS IS THE CASE

This is done with a set of <date_valid_from>: <host_file.tif> pairs in
the run configuration under ['Epidemiology']['Host']['HostRasters'].
This is an optional argument. The 'HostRaster' argument in the
configuration is still needed, but is renamed as 'TargetRaster' to
avoid confusion.

Cocnurrent changes were made in epi model.

This may one day be replaced by some 'host preprocessing' type
of EWS component.

Aspects to improve:

*  Currently, the dynamic host map has to be handled both in
ews-epidmiology for run time, and here for post-run in order
to convert units. It might be neater to do once in one place only
 by moving the unit conversion functionality into the epi model.

 * Implement testing for handling of dynamic host data.

See EpiModel.EpiPrep.updater.update_input() docstring for comments.

This should substantially speed up production epi runs, particularly
towards the end of the season.

This commit also unifies deposition and env suit preparation code.