Implemented rrule session creation
[models] Added dtstart and duration to rrule object.

[models] Fixed the time comparison login

Fixed the time comparason between datetime with tz and non tz.

[models] Added rrule creation logic.

Added the logic in SeriesFromDict to support rrules, as well as a
RRuleFromDict method.

[controller] Added support for rrule auto-creation

Added the session auto creation when a series is created with an rrule field
specified.

[tests] Added rrule to series_insert test.