Feature/dynamicpolymorphism

This is the first MR in a series to implement #26 (closed).

The solver interfaces use dynamic polymorphism, but currently it is not possible to fully benefit from this feature. We want to allow the user to take full benefit from a dynamic interface for solver/precoditioner/scalarproduct/linearoperator.

The main change is that the category isn't an enum anymore, but virtual method catergory().

This MR contains the following changes:

• new method category() to check for the same SolverCategory of different components at run time. This is a slight drawback compared to the current compile time checks, but it adds a lot of flexibility as we will be able to write factory classes for solvers and compose/exchange solvers at runtime.
• add SolverCategory::category(object) to be be backwards compatible
• add a cmake switch to enable/disable the backwards compatibility
• update solvers to the new interface
• update preconditioners to the new interface
• update scalar products to the new interface
• update operators to the new interface
• update AMG implementation to the new interface
  • remove static dependency of PropertiesGraphCreator on the category

This MR partially incorporates commits from !5 (closed) and !1 (closed).

dune/istl/paamg/twolevelmethod.hh

@@ -291,6 +291,12 @@ private:
       return apply(x,b,1e-8,res);
     }
 
+    //! Category of the solver (see SolverCategory::Category)
+    virtual SolverCategory::Category category() const
+    {
+      return amg_.category();
+    }
+
     ~AMGInverseOperator()
     {
       if(!first_)