Fix missing initialization of $orphan flag for new annotations and
properly account for annotations that do not have IDs in ADD_ANNOTATIONS
and UPDATE_ANCHOR_STATUS actions.

 - Fix ADD_ANNOTATIONS action replacing the first existing unsaved
   annotation when a second unsaved annotation is added
 - Fix UPDATE_ANCHOR_STATUS action not matching annotations without
   IDs (ie. new annotations) correctly.
 - Fix $orphan flag not being initialized for new annotations

Fixes #94