Extract elliptical movement into reusable helper

Previously including Elliptical Movement Mixin
would override MovementStrategy#move method.

Now defined #move_elliptical similar to #move_linear and uses
that in the EllipticalStrategy move method.

Also adds centralized include for elliptical mixins
Rework Follow Strategy to maintain distance from target

Incorporates a few related changes including:

- removing the point_to_target flag
- handling case which target speed is slower than locations
- orbiting around target when in the vicinity

Specs need to be updated to reflect new functionality
Allow client to specify movement strategy in manu::follow

Now user ships may follow targets via traditional follow or
figure8 movement strategies
Figure8 Strategy: reduce linear speed when rotating
UI: set weapons class on ship init, use to set strategy on attack

JS client will now set ships with 'light' weapons classes to
figure8 strategies while 'heavy' weapons classes will 'follow'
their targets
Update a few config values for consistency

- attack distance
- follow distance
- visited trail length (tmp for enhanced debugging)