main-window: Always exit preview when pressing escape

We already have other keybindings for fullscreen; don't mix the two.

Original patch from Cosimo Cecchi for gnome-documents.
main-toolbar: Set column spacing on the center container

Instead of using a margin on the detail label; this ensures the spacing
stays constant even with RTL containers.

Original patch from Cosimo Cecchi for gnome-documents.
collection-manager: Fix typo
organize-collection-view: Fix typo
organize-collection-model: Fix typo
Style fixes
organize-collection: Special case OK clicks when typing a collection

See the comment in the code for why this is necessary, but in a
nutshell, GtkCellRenderer will emit editing-canceled as soon as any
button is clicked (since we focus out of the editable in order to
click the button), and we don't want "focus-out" to mean "cancel" if
we clicked on the OK button.

Original patch from Cosimo Cecchi for gnome-documents.
gd-main-view: Use item ID and not coords to track button press/release

We only want to use click events where press and release are on the
same item - use the item ID to track this invariant rather than the
event coordinates, since a click sequence is valid even if we moved
over the same element.

Original patch from Cosimo Cecchi for gnome-documents.
gd-main-view: Remove unused variables

Original patch from Cosimo Cecchi for gnome-documents.
main-toolbar: Use a ClutterBoxLayout inside MainToolbar

Right now, just pack the GtkClutterActor inside it.

Original patch from Cosimo Cecchi for gnome-documents.
selection-toolbar: Add a tooltip for the Print button

Original patch from Cosimo Cecchi for gnome-documents.
main-window: Switch to overview with BackSpace

Also make Escape switch back to overview only if we're fullscreen.

Original patch from Cosimo Cecchi for gnome-documents.
gd-main-toolbar: Make it a more generic toolbar container

Instead of making assumptions of the desired layout/mode switching of
the clients, just provide a generic container/like interface.

Original patch from Cosimo Cecchi for gnome-documents.
main-toolbar: Update for GdMainToolbar changes

Original patch from Cosimo Cecchi for gnome-documents.
main-toolbar: Implement set_toolbar_title
main-toolbar: Implement active_changed
main-window: Also switch back to overview on Alt+Left

This is consistent with other applications.
main-toolbar: Reverse the back icon when using an RTL layout

Original patch from Cosimo Cecchi for gnome-documents.
utils: Add photos_utils_queue_thumbnail_job_for_file_async

Added gnome-desktop-3.0 to the list of build requirements.
utils: Add a comment about the origin of the code