ACCUMULO-2501 Add deepCopy to RowFilter

Adds a base implementation of deepCopy to org.apache.accumulo.core.iterators.user.RowFilter which sets the iterator source and decisionIterator prope This allows custom RowFilters to be chained together with minimal extra effort.

Signed-off-by: Josh Elser <elserj@apache.org>
ACCUMULO-2501 Fix some formatting and add an explicit test for deepCopy on RowFilter
ACCUMULO-2948 Use an AtomicInteger to any worry from multiple threads access pdCount concurrently.