This is needed in cases where the ElementResponse needs
additional arguments in the construction.

New structure builds and runs, but output is not correct

For consistency, the OSKAR files and classes are renamed to Oskar. The
ElementResponse is now stored in a shared_pointer, rather than in an
unique_ptr.

The implementation is not complete, the coeffficients are missing.

The Hamaker model is currently the only supported model. Two other
models, LOBES and Oskar are added to the enum of models, but are not
implemented yet. To maintain backwards compatability, the default
behavior is to use the Hamaker model.

This way, the ElementResponse object is initialized only once (for HBA
and for LBA), rather than for every station.

* added common reference position for ITRF Direction conversion
* merging changes in CMakeLists
* fixed reference station issue in itrf conversion, plus NCP related bugs
* Some small consistency fixes, some clean-up and adding 'final override' where relevant