Refactor craft building and launching.

This commit only moves the build and launch code out of WindowGUI() and
into its own function BuildAndLaunchCraft().
Factor out resource usage from craft building and launching.

This commit only splits the resource usage code out of
BuildAndLaunchCraft() and into UseResources().
Remove the Kerbal removal code.
Use resources immediately after building the ship.

It might be an issue only while everything is exploding, but this feels
better anyway. Build ship, use resources, launch ship. Should really use
the resources first, but to do so, we need a ship to know what resources to
use...
Clean up the call to AssembleForLaunch().

Make things a little easier to read.
Remove a dead line.
Make a copy of the pad's transform.

It seems that transforms are all by reference, as adjusting the transform
position was causing the pad to jump.
Clear the vessel's Landed flag.

It seems the ship being forced to ground is due to the landed flag being
true when physics kicks in. This breaks the landedAt setting, but oh well.

The explosions are fixed (the craft now sits nicely on the pad when
SpawnHeightOffset is set appropriately), but there are still problems with
control input.
Fix the spawned craft's flag.
Unstick the controls on craft spawn.

Many many thanks to Snjo (author of firespitter) for his help on this. Now
staging and controls work, but unfortunately, the throttle still gets stuck
for me.
Use LANDED instead of PRELAUNCH.

For whatever reason, KSP does not like the ship when in the PRELAUNCH
state. Probably some other vessel state issue, but LANDED seems to work. I
successfully crashed my test ship over 100m from the launch pad :)
Merge pull request #36 from taniwha-qf/pad-fix

Pad fix