directory optimization with compression and reattemp

• Refactor sfind so it can use SLURM_ environment variables to ask to different servers.
• Create a sample bash script to gather all the info (map->reduce)
• Compress directory data with zstd.
• Make a new config.hpp option for controlling the compression
• If directory buffer is not enough it will reattempt with the exact size
• Issues related : #372 (closed) , #371 (closed) , #370 (closed)