update submission examples for slurm, rename, add very brief readme, purge redundant

[water-e]

The submission script examples are nice I didn't know about it because the name of the name linux. How about 'linux_cluster'?

Please rename the directory, add names or subdirectories for slurm and pbs, document in a readme that these came from our hpc4 and hpc5 since this will be helpful for context and for DWR users (but don't use them in the name because outside users won't be able to understand). Then purge possibly conflicting documentation on confluence and point here instead (except hpc5 which is so new).