Connect Master Plan editing with the database

Now that the MasterPlan editor as well as the database representation of the plans are finished, a way to save, edit and see saved plans needs to be created.
This means a save button needs to be added to the editor.
The current /master route needs to be replaced with a feed of master plans, potentially just the own user's plans to begin with.
The saved plans should be editable in the same editor as they are created in.