Order-Mgr: Harmonise and extend OrderController/Mgr

[katharinabassler]

In the Order Manager, both OrderControllerImpl.java and ProcessingOrderMgr.java are in need of harmonization. GetOrders() and GetAndSelectOrders() have the same purpose, but different parameters, which potentially leads to confusions. In order to implement #169, two different, overloaded count methods would have to be implemented, which would lead to further problems. Therefore, two tasks result:

(1) First, harmonize the existing methods.
(2) Second, restrict the number of retrievable records (cf. #169).