NC multiprojectors in UPF v1

[Alexandr Fonari]

Multiprojectors for NC PP are supported by QE:

It is possible to generate PP's by pseudizing atomic waves, i.e. regular solutions of the radial Kohn-Sham equation, at any energy. More than one such atomic waves of different energy can be pseudized for the same l, resulting in a PP with more than one projector per l (directly produced in the separable form). Note however that the implementation of multiple-projector PP's is correct for US pseudization: NC pseudization is not properly done (a generalized norm-conservation requirement is not accounted for). US pseudization is achieved by setting different NC and US pseudization radii...

From here: http://www.quantum-espresso.org/wp-content/uploads/Doc/pseudo-gen/node8.html

I think in the libpspio they are not allowed, and the check is here: upf_read.c/upf_read_nonlocal:
   CHECK_ERROR(ii == jj, PSPIO_EVALUE);

Maybe introduce another error code for that, not PSPIO_EVALUE ?