add wire/edge methods position_at, tangent_at, location_at to class Curve

[jdegenstein]

Currently the operators @, %, ^ for position_at, tangent_at, location_at are bound to class Curve but the actual methods position_at, tangent_at, location_at are not present

[gumyr]

Please hold off on this. As part of the refactoring of topology.py (Issue #788) Curve is changing. Still needs some verification but a Curve that can be a Wire is converted to one during the + operation so all the normal Mixin1D methods work for them. If the Curve consists of disconnected Edges then it will be a Compound and these operations don't apply.

[jdegenstein]

Makes sense, and sounds good -- I started working on it briefly and then realized I was creating more entanglements so I stopped.