allow moving endpoints of a street to determine length, rotation and position

[kfarr]

if managed-street entity selected, then in addition to the transform gizmo there is a new gizmo such as endpoints;

this gizmo will show 2 solid color (cyan) circles, facing up; circle1 at the start of the street and one on the end of the street; the radius could eventually be calculated in the same manner as the gizmo to stay same size relative to screen size, but for now it could be rather large circles of radius such as 3 meters;

similar to a move gizmo 2 axis plane translate, with click and drag the dot will move along the ground plane; the position, length, rotation of the street will be adjusted when clicking and dragging; position of street should be the centerpoint between the 2 points; rotation of street should match the angle of the line that intersects both points. position and rotation can be updated on each tick.

at first start with an implementation that is only adjusting the position and rotation of the street, length adjustment can wait for later. length will be calculated as the distance between the 2 points. however it might not be possible to update length each tick because redrawing street with new length is an expensive operation; not sure how to deal with that yet.