GEOMESA-191 Implement deleteSchema for featureType

deleteSchema removes both metadata and the 3 tables per feature type. Also
checks to see whether or not it's an older 0.10.x table, and if so, uses
the AccumuloFeatureWriter's remove() function to remove rows from the table.
Interesting.  I didn't realize you could re-use a scanner that points to a table that has been deleted without incurring some sort of exception.