Batchifying the calculation of the commutator of the position operator and the DFT+U(+V) term. This allows to compute the current fully batchified.

Avoid potential integer overflows when computing the product of
pack_size along its dimensions or with other, potentially large numbers.
Add some more low-level routines to allow calling with i4 and i8
integers.

For large batch sizes, the multiplication of the number of grid points
with the number of states in a batch could overflow. Change the
integers involved to 8-byte.

- protect other calls of phzeev for matrices of size one
- adapt some code style

The main thing was to fix the get_points and set_points methods to allow
for spinor-type wavefunctions. Moreover, some blas calls needed offsets.

Use 8-byte integers throughout the code for global array sizes and
indices. This in principle enables grids with more than 2^31 points.
Large grids have not been tested yet, first I need to make sure
it works for all the tests in the testsuite.

Implement the local potential kernel for complex potentials for all spin
cases and use it in the right place.

With this change, we now use well-defined kind parameters instead of the
non-standard 8.

Also change integer(4) to integer(i4). This makes the code more portable
and adhering to the Fortran standard.

Change the order of arguments in messages_print_stress to match other routines.

Add space between some keywords (if, case, then) and parentheses, so that the code resembles written human language more.

Removed several nullify routines. Also made sure that several subroutines that copy derived data types that do not have a finalizer call the corresponding *_end routine explicitly and have the corresponding argument is intent(inout).

Remove the INCR macro in order to stick as much as possible with Fortran, so that the code is not too much obfuscated.

The packing for sending and unpacking from receiving is done with a
kernel that implements a general reordering according to a map.

The implementation again supports both normal MPI and CUDA-aware MPI.

Replace real(8) by FLOAT when possible.
Remove some single precision routines, as this is not supported anymore