DELAY option, export parameter

Some configurable options in Autosubmit, such as RETRIALS or SPLITS, among others are stored in the parameters dictionary so that the value can be read at any time from templates. DELAY should similarly be included in parameters just below this line:

https://earth.bsc.es/gitlab/es/autosubmit/blob/master/autosubmit/job/job.py#L590

The following page of the documentation must be updated with DELAY variable, in job variables section:

https://autosubmit.readthedocs.io/en/latest/variables.html

@mcastril @gmontane