Relaxed view restriction so you can move left/right in the cabin but not forced upwards

Added a power-twin configuration as they were in operation and delivered as such from 1957, see for example 50869+50922.

Release version.

This is mostly a class 117 based model with the following changes:
- Factory livery
- 4 (working) lights (117 had none)
- small destination box instead of 4-digit headcode
- BR 'Lion' crest
- Whiskers
- No stripes
- Double doors to guard van
- Handrails for access to cabin
- Single Wiper (driver's side)