Improve filtering to use smaller dependencies if available #2
Description
Currently the filtering module always grabs the files from base-csv to filter from. However, if a time range is given that is subsumed by another filtered file in filtered-csv, that file could be used instead. For instance, if we need to filter to 2011-2011, we can do that with the dataset for 2010-2012, since 2011 is subsumed by it.
This should be implemented for all YearFilterableTask subclasses (so probably something generic on the base class).