Added libgd submodule
Updated docs to reflect the changes.
Added initial changes to GcalWindow

Replaced GcalToolbar for GdHeaderBar
Commented out code for ensure building
Updated authors
Initial GdHeaderBar migration
Updated docs: Planning
Removed ClutterActor from main UI

Use GtkSearchbar
Updated Notification system to new UI

Still mising here some way to solve the stacked notifications issue.
Removed internal copy of Notification widget.

Use GdNotification
ui: Removed GcalToolbar and GcalSearchbar
app: Fixed string in --version handle
ui: connected new-event button

It's just the connection what has been updated, since the
widget is still working with clutter there's no visible
effect when clicking [New Event] button

[New Event] button changed to text button, and updated
style

Removed non-needed code
docs: updated

Removed stuff already done.
ui: migrating from GdHeaderBar to GtkHeaderBar
ui: use GtkStack instead of GdStack
ui: reverting hack made for GdHeaderBar
ui: Updating to GtkSearchBar new API
ui: Removed Clutter from GcalEventOverlay

This commit got mixed in, and that's why you will
see warnings. Future commits will fix this.
This one builds, though.
build: Added gresources to binary

GcalNavBar ui added as a resource.
ui: Added GcalNavBar widget.

GcalNavBar widget is composited using templates.
Great work of Tristan Van Berkom <tristanvb@openismus.com> on
using this.