first compiling version of tbb-enabled assembly
[assembler] splits Functor/ApllyOn namespaces into sep header
[assembler] splits GridWalker Wrapper classes into sep file
[assembler] IndexSetPartitioner moved to Stuff
[assembler] splits the local wrapper classes into sep file
[assembler] indent/include cleanup
[assembler.walker_wrapper] added Codim0LambdaWrapper

Not tested^^
[assembler.gridwalker] added add() for codim 0 lambda

Not tested^^
[assembler] put ApplyOn back to functors
[assembler.functors] updated typedefs
[assembler] moved walker_wrapper.hh -> walker.hh
[assembler.wrapper] put into internal namespace

There should be no need for users to touch them.
[assembler.gridwalker] updated includes
[assembler] moved local_wrapper to wrapper
[assembler] moved gridwalker, functors and wrapper to dune-stuff
[spaces.cg.base] update to the 21st century^^
[spaces.constraints] added ConstraintsInterface

* put all in Spaces namespace
* renamed LocalDefault -> internal::Default (not intended for end-users)
[spaces.interface] updated local_constraints()
[assemlber.wrapper] updadet constraints usage
[spaces.cg.base] updated constraints usage