Merge feature_FetchUtils branch into develop

This merge will add a modified version of aburrel's fetchUtils.py file into pydarn/sdio/.  The functions within fetchUtils.py will be able to completely replace the currently used file fetching code contained within radDataRead.py and sdDataRead.py such that the need for institution specific directory structure and file naming formats will no longer need to be hard coded.

Here is some an example of how to use the fetch_remote_files function:

pydarn.sdio.fetchUtils.fetch_remote_files(datetime(2013,4,2,0), datetime(2013,4,2,7),'mcm','fitacf','sftp','sd-data.ece.vt.edu','data/{year}/{ftype}/{radar}/', '/var/tmp/', username='sd_dbread', password='5d',channel='b')