add list of default categories

Signed-off-by: Georg Ehrke <developer@georgehrke.com>

Add PropertySelectMultiple

Signed-off-by: Georg Ehrke <developer@georgehrke.com>

Add Categories to EditorSidebar

Signed-off-by: Georg Ehrke <developer@georgehrke.com>

Add category indicator to calendar-grid

Signed-off-by: Georg Ehrke <developer@georgehrke.com>

Revert "Add category indicator to calendar-grid"

This reverts commit d71a70ee6a43cc3e103ee6dfe61aa9a282c76953.

Signed-off-by: Georg Ehrke <developer@georgehrke.com>

Read-only version of category picker

Signed-off-by: Georg Ehrke <developer@georgehrke.com>