Dev

This merge request include :

• multiple simultaneous computations
• better management of memory (do not open data without request)
• allow using singularity image on local computation. If swaf_core object is instancied in a singularity image too, it is not possible to use an other singularity image.
• add a compute widget allowing easy monitoring
• default computation directory on servers
• fix an error if byobu is active by default on computation server
• fix relative import