[common.fmatrix]

* let the default ctor do the same as the base classes one
* remove obsolete operator=
* explicitly state two ctors for both FieldVector variants in < ..., 1, >
  specialization (why oh why, clang?)
* remove ambiguous operator* in < ..., 1, 1 > specialization
[la.container.pattern] fixed nasty copy-paste bug
[common.fixed_map] fixed several bugs

The const variant of find() did never compile bc of the missing *this. In
addition the getIdx(key) would have returned -1l for a missing key while
the ctor of the const_iterator expects a std::size_t. To resolve this
situation I changed getIdx to return a std::size_t and return N for a
missing key which is in line with the overall syntax in this class
concerning end() iterators.
disabled some warnings
[test] added errors_are_not_as_expected exception

Also rearranged some includes. Now we just disable warnings for all dune
modules that are not ours...
[cmake] remove -O? from debug cxx flags

At the moment it is not trivial to configure a debug build with e.g. -O2.
Upon calling make cmake is called and the CMAKE_CXX_FLAGS_DEBUG are
appended to any given CMAKE_CXX_FLAGS, thus overriding any -O? given there.
Since the desired debug flag might vary from compiler to compiler
(-O0, -Og) anyway I propose to remove the -O? entirely from the debug
flags. Please revert or voice opinions!
[common.fixed_map] updated exceptions
Revert "[cmake] remove -O? from debug cxx flags"

This reverts commit b5e571fc9ad2240d510514566c0946b2cce23426.
[cmake] use CACHE STRING for cxx flags
[grid] use version aware reference_element indirection everywhere
Change grid provider interface

This fixes an issue where unreflected usage leads
to segfault: If &myGrid is passed to grid provider,
the destructor of shared_ptr will try and delete
myGrid, which is usually not desired the behavior.
Merge branch 'master' of https://github.com/wwu-numerik/dune-stuff

Conflicts:
	dune/stuff/common/fixed_map.hh
	dune/stuff/common/fmatrix.hh
	dune/stuff/grid/provider.hh
	dune/stuff/grid/search.hh
	dune/stuff/test/test_common.hh