[discretizations] added first draft to inject a stationary multiscale discretization
[discretizations] added multiscale discretization
[functions.default] added Function::FrozenDefault
[clang-format] added first draft
[dune.pymor.discretizations] updated multiscale discretization
which should rather be a block discretizations at some point
[la.container.eigen] changed EigenDenseVector to COW
[la.container.eigen] changed EigenRowMajorSparseMatrix to COW
[la.container.eigen] fixed missing return
[la.container.dunedynamic] changed DuneDynamicVector to COW
[la.container.dunedynamic] changed DuneDynamicMatrix to COW