Add a (increasing) delay when submitting multiple jobs in a batch

[Nicklas Nordborg]

When submitting multiple jobs at the same time and the cluster has a lot of free nodes, it is possible that all jobs are started at more or less the same time. If the jobs are of the same type (eg. alignment) they may all try to load the same resources (eg. genome index) at the same time. This could lead to overloading network or disk capacity.

Both the Open Grid Engine and Slurm support setting a specified time point for starting a job. We could use this to spread out the batch over a couple of minutes so that all jobs are not started at the same time.

[Nicklas Nordborg]

In 6672:

Fixes #1384: Add a (increasing) delay when submitting multiple jobs in a batch

A new configuration class BatchConfig has been implemented. Each JobConfig will get an instance with a default delay of 30 seconds. It is possible to override this when creating a JobDefinition.

[Nicklas Nordborg]

In 6687:

References #1384: Add a (increasing) delay when submitting multiple jobs in a batch

Fixes a NullPointerException when no config has been specified for a job definition.