Fixes multiple copyright messages in the doxygen docu.

ag '\\file' -L --ignore=ThirdParty *Lib |xargs  sed -i 's/\(.*\)\\copyright/\1\\file\n\1\\copyright/'

If there are no additional members in the MaterialStateVariables,
the default implementation from MechanicsBase is sufficient.

Needed to update the integrateStress return value type.

Same function is used in Ehlers and in the LinearElasticIsotropic.

This allows to store a const reference in the integratio
point data structures.

Clang format run on near-the-header lines.

Happy New Year

Move it from header to impl, which is only included
in the cpp.

This reverts commit 05677165.

Conflicts:
	FileIO/XmlIO/XmlGspInterface.cpp
	README.md

- added test programm for solving a linear system with CG-method
- time measurement is at the moment OS dependent!
- added Base folder
- added GeoLib folder
- added files in MathLib folder - restructured MathLib folder

- applying changes to interfaces