Added function for adding meta-information.

This adds a new section to the datafile. Problem is this is explicit to
the Schrodingerfunction problem. It is optional, so saving can still be
used for all problems. Yet this will give a generic eigenvalue file.
Could make this parameter thingy general by giving as list with key and
value?
Added usage of physical params function.
Added sorted eigenvalues for compulsory tests.
Added eigenvalue data.