deskutils/gnome-planner: resurrect Gnome Planner

Gnome Planner is a cross-platform project management tool
based on the Work breakdown structure (WBS).
You can visualize project in time using Gantt chart, list
the complete breakdown of your project along with the
estimated cost and effort and manage your resources assignments.

This port is based on head branch of the project which is a WIP
version of the future GTK 3 port. This version also integrate
multiple fixes.