Create repository for NextSim

[draenog]

Currently we obtain NextSim by downloading tarball from source files from goodl drive. If we need to adapt them to compile NextSim on Mahuika we may need a git repository where we track our changes.

[rafacsantana]

agree

[draenog]

I create repo a https://github.com:ICCS-NextSim/nextsim.git It is a fork of https://github.com/nansencenter/nextsim.git