[cmake] remove DS_OVERRIDE and DS_FINAL

Drop support for override and final keyword discovery since all supported
compiler understand those by now. Further use of DS_OVERRIDE or DS_FINAL
will trigger a compile error.
replaced DS_OVERRIDE and DS_FINAL by override and final, respectively
[test.common_fixed_map] remove wrong DUNE_UNUSED
[test.common_timedlogging] do not use man.hxx

Since the timed logger is by now instantiated in main.hxx to be used in
other tests this test must not use main.hxx but have its own main.
[common] disable_warnings: sync clang ignores to gcc
[cmake] debug flags fixup for icc
[common] fixes a few shadowing warnings
[grid.walker] fixes base classes w/o virt dtors
[common.disable_warnings] corrects gcc guard
makes a bunch of single arg ctors explicit

afaict nothing is relying on the implicit type conversions
[la] adds vectorinterface note
fixes a few more warnings
[la.container] fixes vector-iface hiding cnt-iface operator*=
[la.container] properly implement operator= in all vectors, closes #8
[test.main] circumvent unconditional warning output

The other alternative would be to instantiate the Config() in a way that
there is no default warning.
[common.configtree] remove guard of local header

Those can always be included!
[common.tuple] update include guard
[fem.customprojection] update include guards
[grid.entity] do not guard geometry include with HAVE_DUNE_GRID
[grid.search] guard complete header with HAVE_DUNE_GRID