Replaces the former sole Element entity by two, Sphere and Point, both implementing an Element trait. Adds Point display, uses the former Element display for Sphere. Adds a new "canned" configuration, and the ability to add, select, and nudge Point entities.
Co-authored-by: Aaron Fenyes <aaron.fenyes@fareycircles.ooo>
Reviewed-on: #82
Co-authored-by: Vectornaut <vectornaut@nobody@nowhere.net>
Co-committed-by: Vectornaut <vectornaut@nobody@nowhere.net>
