[la.container.interfaces] fix operator<< friend declaration
[la.solver] let post_check_solves_system default to 1e-5
* otherwise the test in dune-gdt fails for Spe10Model1
[common.crtp] make types and methods public
* this way one can call as_imp() when matching against an interface
[functions.combined] minor change in name of difference
[functions.interfaces] update visualization
* make subsampling optional, but default to it
* make vtk output type optional and default to appendedraw
[la.container.interfaces] derive from CRTP publicly
[functions.interfaces] added operator-
[common.vector] removed obsolete specialization of clear()
[cmake] define HAVE_EIGEN
[la.container.interfaces] disable warnings for dynvector
[test.la_container] rename DuneDynamicVector -> CommonDenseVector
[la.container.eigen] added missing 'return' in non-void dot-function
[test.la_container] added some asserts and added test for operator[]
[la.container.interfaces] added documentation
[test.la_container] renamed check() methods to fulfills_interface()
[test.la_container] added produces_correct_results() method (empty by now)
[test.la_container] added test for correct amax results
[la.container.eigen] fixed amax() method to pass test
[stuff.la.eigen] fixed style
[la.container.interfaces] corrected documentation