I also removed the const of the `grid_view_` member to get rid of the
cast in the `backend_` ctor call. Is this preferable over the const_cast,
@renemilk?

refs #13

refs #13
currently breaks a few copy tests

refs #13
currently breaks FemBased Spaces testing due to GridPart/View types
snafu

This should ensure that all spaces have a sane copy and move ctor and
forbid copy and move assignment. In addition all spaces have proper
communicators now.

Paragraph 12.8/15 of the C++11 Standard:

The implicitly-defined copy/move constructor for a non-union class X
performs a memberwise copy/move of its bases and members

* there seems to be a bug in dune-commons FloatCmp, so instead of testing
  against 0 we add 1 on both sides
* the basis functions are extremely sensitive to local coordinate
  distortions, so we obtain the (entity) local vertex coordinates from the
  reference elements instead of the entities geometry's local()

* ContinuousLagrangeSpaceBase -> Spaces::ContinuousLagrangeBase
* ContinuousLagrangeSpace::FemWrapper
  -> Spaces::ContinuousLagrange::FemBased
* ContinuousLagrangeSpace::FemLocalfunctionsWrapper
  -> Spaces::ContinuousLagrange::FemLocalfunctionsBased
* ContinuousLagrangeSpace::PdelabWrapper
  -> Spaces::ContinuousLagrange::PdelabBased
* DiscontinuousLagrangeSpace::FemLocalfunctionsWrapper
  -> Spaces::DiscontinuousLagrange::FemLocalfunctionsBased
* RaviartThomasSpace::FemLocalfunctionsWrapper
  -> Spaces::RaviartThomas::FemLocalfunctionsBased
* FiniteVolumeSpace::Default
  -> Spaces::FiniteVolume::Default