Expand order search handler to support searching on Accession Number and Order Number

In TRUNK-5738 we will be expanding order searching in core to allow searching by accession number and order number. This needs to be supported RESTfully as well.

If we only backport TRUNK-5738 to Core 2.3.x, we will likely want to create a OrderSearchHandler2_3 that delegates most of it's functionality to OrderSearchHandler2_2.

This also likely means, unfortunately, making the 2.3 sub project rely on core 2.3.1-SNAPSHOT.

We will likely want to do a 2.3.1 release of Core after making this change.