ETABS_Toolkit: add Create Uniform Load Set

[JosefTaylor]

Description:

ETABS has Uniform Load Sets which are very useful in creating buildings with typical loadings. These coordinate well with load maps in Revit. We would create in the ETABS oM a new object containing a list of area loads (with no objects set) or a list of loadcases and pressures. Only gravity loads are allowed.

Similar to https://github.com/BHoM/RAM_Toolkit/issues/91

[mchaf]

Uniform load sets are critical to any loading workflows for ETABS, and I am happy to help test this as appropriate

[JosefTaylor]

This might be a candidate for trying to push things through the Interactive Database, as CSI hasn't produced an API method for UniformLoadSets