[pg.spaces] fewer shared_ptr maps/backends

refs #13
currently breaks a few copy tests
add template parameter ScalarImp to occurences of Matrix/Vectorinterface
add template parameter ScalarImp to occurences of Vector/MatrixInterface
[localevaluation.swipdg] add missing include
[test.grids] add definition of AluConform3dGridType
Merge branch 'master' of https://github.com/pymor/dune-gdt
[space.cg.tools] deref. layers to copy
[spaces] fixes remaining copying issues wrt ptr

refs #13
Merge branch 'master' of https://github.com/pymor/dune-gdt
[assembler.system] passing gridView by value
[test] fixes override final usage
[pg.dg.fem] fixup gridpart constnesss
Merge branch 'master' of https://github.com/pymor/dune-gdt
[assembler.local.codim1] added Codim1CouplingOperatorAccumulateFunctor
[products.swipdgpenalty] added first draft to playground
[products.base] added coupling operator to LocalOperatorProviderBase
[products.base] updated documentation of LocalOperatorProviderBase
[products.base] added coupling operator to LocalizableBaseHelper
[products.base] added compute_locally()

This is required to allow access to local results, i.e. in the context of
error estimation.
[products.base] added coupling operator to AssemblableBaseHelper