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>

Conflicts:
	core/src/test/java/org/apache/accumulo/core/iterators/user/RowFilterTest.java
ACCUMULO-2501 Fix some formatting and add an explicit test for deepCopy on RowFilter

Conflicts:
	core/src/test/java/org/apache/accumulo/core/iterators/user/RowFilterTest.java