recent-view: Fix build when libgnome-desktop is not available
libdocument: Add remove_annotation to DocumentAnnotations.

https://bugzilla.gnome.org/show_bug.cgi?id=649044
libview: add ev_view_remove_annotation

Hide annotation windows if necessary and unset selected
element before removing an annotation.

https://bugzilla.gnome.org/show_bug.cgi?id=649044
Add Delete Annotation option to the view popup

Based on this patch:
https://bug649044.bugzilla-attachments.gnome.org/attachment.cgi?id=275731
by Jose Aliste.
Adapted to the new menu.
libdocument: add ev_mapping_list_set_remove

Needed to remove annotations from a mapping list

https://bugzilla.gnome.org/show_bug.cgi?id=649044
pdf: Implement remove_annotation virtual func

https://bugzilla.gnome.org/show_bug.cgi?id=649044
Refreshing annotations' sidebar upon deletion

When an annotation is deleted, the sidebar needs to
be refreshed so that the annotation is removed from
the list

See item 3 in this comment:
https://bugzilla.gnome.org/show_bug.cgi?id=649044#c33
Selecting new annotations

After deleting all the annotations of one page,
adding a new annotation is recognized by evince
and can be selected.

Item #1 of:
https://bugzilla.gnome.org/show_bug.cgi?id=649044#c33
Making annotations names unique

Naming the annotations sequentially by number is
problematic when they can be removed (see
https://bugzilla.gnome.org/show_bug.cgi?id=649044#c33).
This patch changes the annotation names to
timestamps, guaranteeing that they are indeed
unique.