Limit compute available for each session

[ChrisWellsWood]

Currently, a user could dump 1,000 structure files with 1,000,000 residues each into de-stress and the server would fall over. Although I trust our future users, it's probably not ideal behaviour. There are a few ways that we can tackle this:

1. Limit the number of files that can be running on the server for an individual session
2. Limit the number of residues allowed in a structure file
3. Add a time limit to individual jobs running on the server

These are not mutually exclusive and I think we should probably use all of these.

[ChrisWellsWood]

@MichaelJamesStam ran a test where he tried to load 400 models into the application and the UI became unresponsive. This could be due to the debugger. Worth investigating to determine if we can improve this.

[ChrisWellsWood]

One solution would be to throttle job submissions client side if too many jobs are submitted, rather than flooding the queue.