[functions.checkerboard]

* use Common::FieldVector in ctor (is convertible from Dune::FieldVector
  and std::vector)
* forbid assignment
[aliases] removed DSLA, aka LA::Algorithm (does not exist)
[common.configuration] added meaningful error message
[function.indicator]

* added ctor for Common::FieldVector
* adapted signature to the rest of the functions
[functions.spe10] added ctor taking FieldVectors
[la.container] set default backend to eigen

Istl is not reliable enough (might be faster but solves less systems with
default settings).
[functions.spe10] minor updates
[common.configuration] added ctor taking an istream
[functions.combine] added Product
[functions.combined] added make_{difference,sum,product}()