add a template class of Gauss quadrature for regular shape elements, i.e. line, quad and hex
add TestFemIntegration
[IntegrationGaussRegular] getPoint() -> getWeightedPoint()

Changed also the return type from std::tuple to std::array.
Using TemplateWeightedPoint in class IntegrationGaussRegular.
[NL] small improvements in gauss regular integration.
[MaL] Move GaussLegendre coeff. definitions in cpp.

Also remove repetitive order definitions.
[NL] IntegrateGaussRegular: Add assert on index and integration order.
[NL] Update for compile-time GaussLegendre integration.
[NL] IntegrateGaussRegular: refactor GaussLegendre calls.
[NL] Replace initializer-lists with explicit assignments.
[NL] Create template version of getWeightedPoint().

Reduces code duplication. Allows later extension towards TMP.
[NL] Rename sampling to integration order.

Also rename other variants of integration order.
[NL] Add WeightedPoint typedef.
[NL] Rename getPosition() to getPositionIndices().