Updated the run scripts to generate the ICs if they are not present. Removed the outdated global 'run.sh' script.

Added a command-line option '-d' to execute a dry run which read the parameter file and opens the ICs to check whether everything is OK.

Parallel gpart sort

That's essentially a copy-paste of the part version. 

Indices are still of type `size_t` to be compatible with the rest of the code. We can move to `int` later on.

See merge request !128