RAD-292 Generate accessionnumber (#355)
Generate an accessionnumber for radiology orders in same approach chosen by
order entry for orderNumber.
* add global property for accessionnr seed
* add accessionnr seed in config.xml (validated as regex so we only get digits)
* fix testdatasets for new global property
* remove unused obs row from testdatasets
* add AccessionNumberGenerator interface
* RadiologyOrderServiceImpl implements AccessionNumberGenerator
* add HibernateRadiologyOrderDAO method to get next accessionnr seed
* add HibernateRadiologyOrderDAOTest
* add test for placeRadiologyOrder
* show accessionnr in RadiologyOrderResource getDisplayString()