Write "Getting started" chapter

Add a getting started chapter to the manual explaining:

• how to apply for an account iet-support@ost.ch (Florian & Reza)
• connecting over ssh (with PKI) for windows in powershell
• (explaining the folder structure of the cluster) home folder (/home/OST, project folder (/home/pool)
• using module files (load, purge/unload, avail)
• submitting a simulation over SLURM (sbatch, srun)
• checking for job status (sacct, sreport)
• (mounting a samba share in linux (and windows)) accesing your data locally... (sshfs)