Add implementation for query select results.
Change worktype enum for distinguishing between different select types.
Add methods for getting and setting work type.
Add another worktype enum value for distinguishing between three different select types.
First reimplementation of select process in database worker.
Implementation of query results.
Comment out non working code.
Change namespace of sql work and result types.
Forward declarations.
Implementation of different sql select work types.
Make method virtual.
Initiate selection work.
Merge branch 'treeview-selection' into develop