Represents the importance of an annotation.
Possible importance levels include, in order from less to more important: Trivial, ExtremelyUnimportant, VeryUnimportant, QuiteUnimportant, Unimportant, SlightlyUnimportant, Neutral, SlightlyImportant, Important, QuiteImportant, VeryImportant, ExtremelyImportant and Critical.
Importance properties belong to the following property types: "ImportanceProperty","ClassifyingProperty"