Merge branch 'feature/algorithm-integrate-and-findroot-scalar' into 'master'

dumux/common/doubleexpintegrationconstants.hh

dumux/common/doubleexpintegrator.hh

dumux/common/geometry/CMakeLists.txt

dumux/common/geometry/refinementquadraturerule.hh

dumux/common/integrate.hh

dumux/nonlinear/CMakeLists.txt

dumux/nonlinear/findscalarroot.hh

test/CMakeLists.txt

test/common/CMakeLists.txt

test/common/geometry/CMakeLists.txt

test/common/geometry/test_refinementquadraturerule.cc

test/common/integrate/CMakeLists.txt

test/common/integrate/test_integratescalar.cc

test/nonlinear/CMakeLists.txt

test/nonlinear/findscalarroot/CMakeLists.txt

test/nonlinear/findscalarroot/test_findscalarroot.cc