glib: Add demo for simple line annotations
glib: Aggregate showing individuals widgets as one single show_all
glib: Aggregate individuals widgets as one single show_all
glib: Move add annotation type to main widget

Prepare the way to add an annotation by interacting directly with
the drawing area instead of entering the coordinates by hand. The
first step is move the interaction to the main annotation widget.
glib: Add annotations interactively

Prepare the render area to add annotations interactively instead
of button/dialog.
glib: Remove button to add annotations with a dialog

Instead, the annotation will be added interactively in the render
area.
glib: Merge type and color columns in annotations demo
glib: Add method poppler_annot_get_rectangle

Annotation objects contain at least two keys, Rect and Subtype.
The former has the coordinates where the annotation is placed.

Signed-off-by: Germán Poo-Caamaño <gpoo@gnome.org>
glib: Use a generic color chooser for new annotations demo

Set the color before adding an annotation instead of assigning
one by default and allowing a later modification.
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 PopplerQuadrilateral boxed type
glib: Add PopplerAnnotTextMarkup object

Signed-off-by: Germán Poo-Caamaño <gpoo@gnome.org>
glib: Add PopplerAnnotTextHighlight object

Signed-off-by: Germán Poo-Caamaño <gpoo@gnome.org>
glib: Add PopplerAnnotTextUnderline object

Signed-off-by: Germán Poo-Caamaño <gpoo@gnome.org>
glib: Add PopplerAnnotTextSquiggly object

Signed-off-by: Germán Poo-Caamaño <gpoo@gnome.org>
glib: Add PopplerAnnotTextStrikeOut object

Signed-off-by: Germán Poo-Caamaño <gpoo@gnome.org>
glib: Add references in poppler-sections

Signed-off-by: Germán Poo-Caamaño <gpoo@gnome.org>
glib: Add save to file in demo

Useful to save PDF with annotations and compare the resulting file
later.
glib: Add support for PopplerTextAnnotMarkup to the demo
glib: Move the annotation's rectangle to properties in demo

This allows to make the list view of annotations cleaner