ETABS_Toolkit: Mirrored asymmetric sections

[kThorsager]

Description:

The current ETABS API does not support mirroring sections even tho it is possible within ETABS.
As ETABS also flips bars it does not like (#232) which will mirror the section, without any way to maintain consistency.

A bootleg temporary solution would be to always create two sections when the are asymmetric assign properly and infer which should be mirrored in ETABS by naming.
i.e. L 200x150x18.0 and L 200x150x18.0_Mirrored
slightly manual but would enable a workflow