Bug 5395: Update C4::Acquisition::SearchOrders POD

Bug 5395: Update C4::Acquisition::SearchOrders POD

Comparing the perldoc to the function:
- basketname
- basketgroupname
- budget_id
Were missing. This adds them.

Also, a description of ordernumber and search were
added, as they are not self-evident by their name
alone.

There are no code changes, so all tests should pass
or fail identically before and after patch.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Fixed typo basetgroupname

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Mason James <mtj@kohaaloha.com>