Builder: support jobs to automatically change stages

[melisabok]

For example: when close submission is at night programate a job to execute the close submmission automatically.

[mspector]

Before we create jobs like this, we should fully implement the logic of all the various "date" fields in the invitation, note, and group objects. Doing this would solve many (but not necessarily all) of the timing-related issues. For example:

• Create comment invitations in advance, but with cdate set to a time in the future when commenting is enabled.
• Create revision invitation in advance with cdate set to the end of the review period (in this example, authors are allowed to revise papers after they've been reviewed).
• Create two homepage groups A and B, with cdate-to-ddate periods that abut one another (e.g. group A has cdate=0 and ddate=10, group B has cdate=10 and ddate=20, etc.). Group A would have a webfield for the submission stage, and group B would have a webfield for the post-submission stage.

EDIT: regarding the last example involving groups: I'm actually not certain if the spec includes groups among the objects that can be specified like this, but one issue that we might run into is how to transfer members across groups in cases like these.