If CVODE_FOUND is not defined the cvode code is excluded.

All input arguments and return values are now MappedVector
or MappedMatrix (or const). Before it was mixed up
with std::array.

getYDot() now returns a value instead of modifying input
parameter.

This eliminates _handles object in ode solver factory.

Remove setArguments() in cvodefactory.
Provide ctor for Handles.
Make f and df private.

Using Eigen::Map<Eigen::Matrix...>> class seems to
work by default with the sundials storage order and
vice versa.

ConfigTree is not storing the ptree passed through
the ctor.

Enable shared linking

This adds -fPIC to gcc/clang.

When building shared libraries -DBUILD_SHARED_LIBS=On must be passed to the
cmake invokation. Otherwise the default static linking applies.

This reduces the compile time, which is especially interesting for the debug
builds.