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 #358)

Some potential imrpvements:

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