Scripts for getting UNAVCO data updated

The scripts for getting UNAVCO data in daily RDAHMM service are updated to get the data for specified starting and ending dates. They were not working correctly previously because the tools used by the scripts don't return data that exactly match the given dates. They just return the whole data set for a given station if the data set has a overlap with the given time period. Marie added a filtering step in the scripts to cut off the data that fall out of the given date range.