Terminal Burn

• New XT-L-KRAB model to replace the XT-LB, from steedcrugeon. (The old model has been made unresearchable, and will be removed in the next release.)
• Changed SoftLanding calculation so that it no longer fires late in landers with TWRs below 5 or so. Again, be advised that solid rocket motors do not throttle, so there will be a drop after they cut out! Bring airbags, girders, or something crushable to land on...
• Adjusted rearm/settle conditions for landertron box to be less 'bouncy'.
• Added subtle up-arrows to XT-L2, to clarify which way to orient it.