Make Ladder Bed backwalls dependant

[milko7002]

I really like the idea of Ladder Bed, but very rarely see anyone including myself use them. 

I think a small adjustment like making them Backwalls dependant, similar to some of the new machines we got in the aquatic dlc, insted of requiring the foundation would really make them more viable 

[Sasza22]

This would be cool for rockets. Putting it above ground and adding ladders would allow for more flexibility. As for now they don`t save that much space compared to cots unless you stack them vertically.