[common.exception] moven namespace Exception -> Exceptions
* to avoid clashes with Dune::Exception
use new Exceptions namespace everywhere
[common.configtree] renamed add() set()
* set() is now used to set key/value pairs
* add() is used to insert all keys of another instance
* + and += can be used as a shorthand for add()
use new configtree.add everywhere
[functions.spe10] use proper exceptions
[common.exceptions] added linear_solver_failed
[la.solver] changed api
* apply() does not return an error code any more
* each solver is required to throw an appropriate exception in case of any
  errors
[la.solver.eigen] updated EigenRowMajorSparseMatrix solver
* checks are on by default
* use exceptions instead of error codes
* add further comments
[la.container.interfaces] added operator* to ContainerInterface
[la.container.interfaces] fixed several operators
[la.container.interfaces] added operator* to VectorInterface
[la.container.eigen] added EigenBaseVector
* derived EigenDenseVector from EigenBaseVector
[la.solver] whitespace
[la.solver.iegen] updated EigenRowMajorSparseMatrix implementation
* symmetry check does not consume all available memory
* reenabled llt.simplicial and ldlt.simplicial
* reordered defaults
* added notes and verbose error messages
[la.container.eigen] derived EigenMappedDenseVector from EigenBaseVector
[la.solver.eigen] make use of EigenBaseVector
[la.container.eigen] make use of EigenBaseVector
[la.solver.eigen] finished refactoring so far
* minor fixes to EigenRawMajorSparse solver
* reordered options in EigenDenseMatrix solver
* updated EigenDenseMatrix solver to use exceptions
[la.solver.eigen] reorder options in EigenDenseMatrix
[la.solver.dunedynamic] refactor