Feature highlights
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* New plots module to display the cross section properties and its internal loads using Matplotlib methods;
* New examples package and sphinx/readthedocs documentation;
* Added EImax, EIMin and Principal direction angle to section summary;
* Multiple code documentation (docstring) improvements;
Main bug fixes:
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* Fixed a bug incorrectly calculating Nxy for sections with booms;
* Fixed singular matrix cases when using Shear Connectors.