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.
Hmm, this is going to be extremely expensive.  Not sure what the best approach is to deleting these tables though.  Is there a scanner/compaction option that may improve this?