SIRIUS/7.4.0

This pre-release contains the following changes:

• update of the API to pass Fortran arrays natively
• interface with the Exciting FP-LAPW code
• add vc-sqnm library for local geometry optimisation
• fixes in the LDA+U+V implementation for non-magnetic case
• update Python module; drop Python2 support
• refactor Wave_function class; simplify and optimise wf::inner(), wf::transform() and wf::ortho() functions
• introduce output stream; now the output can be directed to stdout, file or buffer
• allow external order of G-vectors
• other minor fixes and optimisations in various parts of the code