Improvements to add_downtime

[GRyall]

• the bullets at the top of the page provide important information, but are not clear.
  
  A change like "to be considered a schedule downtime" and "Current UTC time" along with tidying up the appearance might be good.
• when you click on a site, the affected services/endpoints list is in no apparent order. This would probably be better ordered either by service type or hostname
• I think we should consider defaulting to selecting the site's timezone, rather than UTC.
• On the confirmation page we should offer both site local time and UTC
• The confirmation page would benefit from a back button
• Next to the time setting box, a button which set the start time to "now" may be useful.

[GRyall]

• It would be good if the end time defaulted to the start time.

[gregcorbett]

I think we should consider defaulting to selecting the site's timezone, rather than UTC.

As an alternative to the site's timezone, we could default to the users current timezone (as indicated by their browser) - perhaps displaying the times of the donwtime in UTC and the site's timezone as well for information purposes.

Special care should be taken if/when determing the site's downtime, as the add_downtime page does allow multiple sites to be shown on the page (and one day be selected within the same downtime, see #261). Once the site(s) have been selected on the page:

• if they are all in the same timezone we can use that timezone,
• otherwise, perhaps we cannot reliably detemrine a site time zone.

[GRyall]

I wouldn't support using the users timezone - downtimes affect sites, not the GOCDB user. If I was travelling and accessing GOCDB, I think my expectation would be that I would set the downtime in the timezone of the site, not the one I happened to be in.

Point taken on the multi-site case.