Safe-Guards preventing segfaults for incorrect inputs (python interface)

See merge request !5

throw an error for missing variables and multiple-defined
 variables if variables are passed to the reader interface

explicitly define the stride for numpy arrays

Updated Docs, New default for python module

See merge request !4

allow reading single source rank in py module

add more class methods to py interface, whitespace

non-MPI version for (new) Python interface (only affects new_python)

See merge request !3

allows suprressing the "Read [...] variables ... " stdout logs

always compile a non-mpi version of the python library, which can be loaded by setting the GENERICIO_NO_MPI env variable

python interface updates and balancing option

See merge request !2

CMakeLists and new python interface

See merge request !1