GEOMESA-134: DTG field treatment in package object 'index' not safe

Wrap dtg variables in core.index in Options, since the temporal field in...

Also modify FilterToAccumulo to handle these changes.
If there is no date/time field in the `SimpleFeatureType` -- or if there is a date/time field, but it is not recognized as the date/time field to index -- then there should be no danger from the encoding, because it should be impossible to query by time against the index (if I'm thinking of this correctly), so those encoded time values should be inert.  (You could still query by time, but that would constitute an attribute-only query, not one that used the index.)

I think the warning I would be most interested in seeing is one in which the `SimpleFeatureType` being created contains a `java.util.Date` field, but no user-data hint specifying the date/time field to index has been set.  Otherwise, I'm willing to assume that the user has done what they want:  Provided a `SimpleFeatureType` that has no indexible date/time field.