Surge of productivity.  A few code changes.

TextMenu.Item now has an "id" field, so you can do things like 

```
activeMenu.Find(x => x.id == (int)MJMenu.ExecuteNodeMenu);
```

MechJebRPM now has a Circularize menu (Circularize at Ap, Pe, or in 15s).

There is now a JUtil.GizmoIcons, similar to JUtil.MapIcons.  JSISteerableCamera now uses it.

JSIOrbitDisplay now knows how to show the vessel position @ closest approach icon if it's on the next patch.

JSIHUD now shows a prograde vector on the heading bar and the ladder as a proxy for slip and angle of attack.