Fix: annotations on page

[bwbohl]

• Fix: placement of annotations with annotation icons per measure
• Fix: priority and category filters
• Fix: do not fail annotation filters if either category or priority is not used at all (partly addresses SourceView: hide or gray-out menuitems if they do not contain items or only one item #358)

Some potential imrpvements:

• change classes of "annotation" and "annotIcon"
• push real annotations not the measure boxes that contain them to viewer.shapes annotations

[bwbohl]

merged with 98f15db