[space.continuouslagrange] allow vector valued
* and throw an exception in the relevant methods
  -> this is far from optimal!
[space.cg.fem] allow to be vector valued
[tests.spaces] add vector valued cg.fem
[basefunctionset.interface] update
* use CRTP from dune-stuff
* use types from base type
[basefunctionset.fem-localfunctions] update
* use types from base
* add static error message for wrong dimensions
[discretefunction.default] whitespace
[space.dg.fem-localfunctions] added static errors for wrong dimensions
[localevaluation.elliptic] extended for vector valued bases
[localevaluation.product] extended for vector valued bases
[operator.darcy] added first draft for cg.fem
[test.operator_reconstructions] added darcy operator
* added test for 2d, linear function
[operator.darcy] moved out of playground
[basefunctionset.finitevolume] added vector valued implementation
[mapper.finitevolume] added vector valued implementation
[space.finitevolume] allow dimRange > 1
[product.interfaces] added induced_norm()
[basefunctionset.pdelab] added piola transformed basis
[mapper.pdelab] renamed PdelabPkQk -> SimplePdelabWrapper
[space.cg.pdelab]
* update basefunctionset and mapper signature
* remove continuous()
[space.raviarthomas.pdelab] added first draft of RTN0 to playground