CDK-367: Update id partitioner to support HBase changes.

This adds a new FieldPartitioner method, getType(S), that returns the
class the partitioner produces when given input of class S. This allows
the IdentityFieldPartitioner to use Object as its input and output
class because its class may not be known when the partition strategy is
built. This also adds convenience methods to get the source and
partition type given an avro schema. These methods are now used by Key
and FileSystemDataset.

This also removes the requried partition name for identity fields. If
not given, the partition name will default to sourceName + "_copy". This
is because HBase doesn't need partition names.
CDK-367: Fix toString methods that ignored parameter.
CDK-367: Fix Conversions for Object.

Conversions was testing the expected type using isAssignableFrom, so the
first branch was always being taken because everything can be assigned
to Object. The fix is to test for Object specifically and return the
input object because no conversion is requested. This was exposed by
Marker's getAs function that is using an id partitioner's getType rather
than getType(inType).
Exclude .json files from rat checks for test fixtures.
CDK-367: Update HBase to use new strategy and mapping formats.

Thanks, Adam!
CDK-367: Update maven plugin for new formats.