Send an email when expected sessions are not uploaded on FlatIron/DataJoint

[anne-urai]

Users frequently find out right before the weekly behavior meeting that their training data have not properly uploaded to FlatIron and DataJoint.

Could Alyx check if, 24 hours after a session was created, the corresponding sessions are detected on the FlatIron. If not, send the user a warning email.

Link: https://int-brain-lab.slack.com/archives/CB13FQFK4/p1558954477010400

[GaelleChapuis]

And in the case of multiple sessions not uploading on a given day, group all in one email so as not to flood mailbox.