Update call to AssembleForLaunch for KSP 0.21

KSP 0.21 changed the parameters of ShipConstruction.AssembleForLaunch: the
state variable is now of type "Game" and it now takes a crew manifest list.

I have used HighLogic.CurrentGame for the game state (I do NOT know if this
is correct, but during my testing, I didn't notice any problems I would
attribute to this).

I used "null" for the crew manifest. This seems to work nicely and as a
side-effect, it fixes the launch-pad's magical ability to create Kerbals:
crewed ships are now built without a crew.
Remove the unused "state" variable.
Merge pull request #31 from taniwha-qf/ksp-0.21-fix

Ksp 0.21 fix
Changed SolidFuel density
Add a SpawnHeightOffset configuration field.

Some pads (eg, the Hooligan Labs pad) have their origin at the bottom of
the pad and thus built craft spawn partially inside the pad, causing all
sorts of chaos. This change moves the built craft's start position up a
configurable amount (in meters). The recommended amount a little over the
distance from the pad's origin to its upper surface.

MODULE
{
	name = ExLaunchPad
	SpawnHeightOffset = 1
}
Added debug mode
Merge pull request #32 from taniwha-qf/spawn-offset

Add a SpawnHeightOffset configuration field.