[common.configtree] fixed a lot
[test.common_configtree] finished so far
[common.exceptions] added internal_error
[la.container.dunedynamic] small update
* added another constructor
* added solver support (this might not be necessarry)
[la.container.eigen] small updates
* added almost_equal
* added another ctor to dense matrix
* added solver support (this might not be necessary)
[la.solver] major update
* there is now a class Solver< MatrixType > that is
  specialized for each matrix type
* the solver is selected by passing an option to the
  apply method
[la.solver.dunedynamic] added
[la.solver.eigen] updated to new design
[test.la_solver] updated
[la.solver] no need to be friendly
[la.container.dunedynamic] fixed check
[la.container.eigen] added compile time errors
[la.container.istl] fixed mv
[la.solver.dunedynamic] fixed check
[la.solver.eigen] fixed check
[la.solver.istl] updated to new layout
[la.solver] added istl
[test.la_solver] added istl
[la.solver.interface] removed
[la.container.eigen] update