UI: add optional width parameter to OrbitLine
UI: add planet mesh to position tracker, use _add_orbit_line helper
UI: track camera changes, use cam pos to scale entities (WIP)
UI: implement entity scene_components method and use in canvas

We can now override method to alter scene components based on
any number of conditions.
UI: add independent camera tracker to entity

Position (and rotation if configured) are kept in sync with
position / location trackers. Camera is added to this component
so that other entity scene components can be managed seperately
UI: add ship indicator sprite
UI: set manu_entity mode on camera mode changes

Will be used to change entity graphics depending on camera mode.

Also resolves a TODO loading min scale from config
UI: represent ship w/ indicator in far / mid camera modes

Override Ship#scene_components to only return indicator when
camera is not in 'near' mode. Regular components are returned
when camera is in near mode
UI: add high level indicator component to station
UI: reset cam target when following entity

Fixes issue where cam is facing wrong direction if manually
panned before entity clicked / cam follows it