Version 7.1.0 released (02-March-2023)

This version (Git hash value 5e104a9d...) provides a number of minor fixes and useful extensions as detailed in the following list of tickets:

• #232: Iso-surface plots for 3D-wavefunctions
• #276: Auto-detect Git version hash value
• #277: Symmetric Euler scheme
• #278: Components of electric field
• #280: Code for Lyapunov solver
• #281: Sparsity and cutoff in qm_bound
• #283: Empty potentials, dipoles, etc ...
• #285: Settable initial momenta
• #286: Convergence in imaginary time

Note that our work on #278 now allows for an arbitrary number of polarization directions, i.e. an arbitrary number of components of E-field vectors and dipole moments as well as polarizabilities. Unfortunately, this leads to a tiny backward incompatibility: Now the E-field amplitude must be given as a scalar or a row(!) vector; previously a polar represention in 2-D (amplitude and polarization angle) was used.
Another minor backward incompatibility is due to renaming class +efi.inter → +efi.interp, for consistency with classes 'interp' in package folders +pot, +dip, etc.