Fix up some whitespace issues.
Split the spawn hight code into its own function.

This allows it to be used for both timed and insta-build modes.
Use a separate variable for run-time spawn offset.

SpawnHeightOffset itself is meant for configuring pads that have their
origin inside the model, so it should not be adjusted at build-time.
Add a ScrapMetal resource.

Both rocket parts converters (the workshop and the old thing) now produce
scrap metal (the workshop is back at 90% utilization). The ScrapMetal
output has been set top optional (needs testing) so not having storage
won't stop the process, you just go back to eating the loss. A means of
converting ScrapMetal to Metal is needed.