glib: Fix rectangle calculation for new annotations in demo
glib: Rearrange layout for annotations in demo

Add render area to visualize the annotations per page.
glib: Expand short names for annotations
glib: Auto-update annotation list and render page in demo
glib: Aggregate showing individuals widgets as one single show_all
glib: Merge type and color columns in annotations demo
glib: Prepare UI to add multiple annotations type in demo
glib: Remove button to add annotations with a dialog
glib: Move remove button in annotations demo to a generic place

Move out from Annotation properties to the top. This make better
use of the space.
glib: Add annotations interactively in demo