Ensure the craft's orbit is valid at all times

The delayed setting of the craft's orbit resulted in the orbit mean
motion being 0 thus producing NaN when queries were made about the orbit
(by kOS, Trajectories, Kerbal Engineer etc). Because kOS and
Trajectories went through OrbitDriver, this would result in the craft
getting deleted, potentially wreaking havoc in the code (especially if
Kerbal Engineer tried to access the orbit as well) and definitely
causing consternation for the player (hey, dude, where's my ship?)

Fixes #163

Source/BuildControl.cs

@@ -651,6 +651,7 @@ internal void BuildAndLaunchCraft ()
 			craftVessel.launchedFrom = builder.LaunchedFrom;
 
 			FlightGlobals.ForceSetActiveVessel (craftVessel);
+			SetCraftOrbit (craftVessel, OrbitDriver.UpdateMode.IDLE);
 			builder.PostBuild (craftVessel);
 			if (builder.capture) {
 				craftVessel.Splashed = craftVessel.Landed = false;
@@ -1041,6 +1042,7 @@ public CostReport getBuildCost (ConfigNode craft, string craftText = null)
 			Vessel craftVessel = ro.AddComponent<Vessel>();
 			craftVessel.vesselName = "EL craftVessel - " + craft.GetValue ("ship");
 			craftVessel.Initialize (true);
+			SetCraftOrbit (craftVessel, OrbitDriver.UpdateMode.IDLE);
 			foreach (Part part in craftVessel.parts) {
 				SanitizePart(part);
 				part.ModulesOnStart();