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.
Ah, it checks the memDataCache first when looking for metadata and finds it since the cache wasn't being cleared when removing metadata from the catalog table. I'll update deleteMetadata to also clear entries out of the cache.