New method to read Jaguar eigenvalues

[ericchansen]

This is an issue that was brought up here. However, the major issues in that thread were dealt with. It seemed more appropriate to have this be its own feature.

Basically, it would be great to have a method or option in calculate that reads Jaguar eigenvalues directly.

Currently, -jeigz reads the eigenvectors and Hessian, not the eigenvalues directly.

Below is what PO suggested.

... pick the frequency, convert it to a.u. (factor in my HessMan.py program), square it, and put back the sign, should now be the eigenvalue of the mass-weighted Hessian.

[ericchansen]

Crap, I opened this in the wrong repository. Oh well.