Add time + time zone to CFP opening/closing options

[vmbrasseur]

The CFP setup form in OSEM only allows you to set the date:

Elsewhere, (under Basics on the conference admin), you can set the time zone of the conference:

But not only can you not set the time for the opening or closing of the CFP, the time used under the covers isn't even in that time zone you defined for the entire conference. It appears to by GMT or UTC instead, but it doesn't tell you that.

To help solve this confusion, plus add clarity & flexibility to the CFP process, I suggest:

• Add time setting to the CFP open & close setup form
• Add time zone setting to the CFP open & close setup form, defaulting it to the time zone defined in the overall conference options
• Make sure this time/time zone is stored consistently in the DB (probably in UTC) and displayed consistently in the UI (using the defined time zone).
• Display the date, time, and time zone for CFP closing in all places where this information appears in the OSEM UI, including osem.seagl.org and osem.seagl.org/conferences/$eventcode/program/proposals.

[vmbrasseur]

I've confirmed that the CFP closing date is using 00:00:00 UTC. The current value for it is 2018-07-30 and the CFP snapped shut at the turn of the clock to 2018-07-31 in the UTC time zone.

Had I not increased the closing date by one day on Saturday, suspecting something weird was going on, the 2018 CFP would have closed 7 hours early, which would have been very bad. We would have pissed people off and lost 2-3 dozen proposals.

[AndrewKvalheim]

Upstream: openSUSE#2769