Trajectory link_phases method should support arguments of add_linkage_constraint.

[robfalck]

Proposed feature.

The link_phases method is a simpler wrapper for the more complex but more capable add_linkage_constraint method.
In order to allow the user to control things like the scaling factors for the imposed constraints, link_phases should support the following options and pass them to add_linkage_constraint.

• units
• scaler
• adder
• ref0
• ref
• linear

If connected is specified, then the above options will have no effect.

Note sign_a and sign_b are explicitly left out here, since the intent of link_phases is to provide continuity in value.

Example

traj.link_phases(
    phases=['ascent', 'descent'],
    vars=['time', 'r', 'h', 'gam'],
    scaler=1.0E-3)