CRM-3896 Modify Date - Time selector MINUTES part to expose all 60 minutes

Currently we allow minutes to be selected in 15 minute increments (0, 15, 30...). This is causing problems when activities are edited - esp ones that are auto-populated during timeline inserts (new case / add a timeline).

1. Modify the minutes select field to include 00 - 59 options.
2. I think there are several places in the code where we do some rounding math to force the 15 minute factors. We should probably remove that code at the same time.

Michal sent this "tip":
On this screen: /civicrm/admin/setting/preferences/date (Home › CiviCRM › Administer CiviCRM › Global Settings › Date Formats › Advanced Date Input Settings) change activityDatetime "Minute increment" to 1.

Not sure if that's all there is to fixing this. If so, we'd also need to modify the new install defaults for this preference as well as "fix it" in 2.1->2.2 upgrade.