Add HalfTurnLeft landing stairs basic feature.  - HalfTurnRight, stairs alignment etc. 'fix' added in 'later version' in my local machine not yet in this commit
Add HalfTurnLeft landing stairs basic feature.
 - HalfTurnRight, stairs alignment etc. 'fix' added in 'later version' in my local machine not yet in this commit

Discussion posts :-

https://forum.freecadweb.org/viewtopic.php?f=23&t=29358&sid=bbca78d86eda8a6f8837fc2901d88be7#p240745
https://forum.freecadweb.org/viewtopic.php?f=23&t=29358&start=70#p247814

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