Update calendar export information.

https://github.com/madewithbytes/us_ignite/issues/288

The calendar preserves the timezone of the event created
it also adds relevant information to the ``ics`` file
such as location, description and URL.
Add cancel button to contact user form.

https://github.com/madewithbytes/us_ignite/issues/272

The cancel button returns the user to the profile detail.
Update labels for the add event form.

https://github.com/madewithbytes/us_ignite/issues/286

The labels are more descriptive of the expected value of
the fields.

Conditionally loading the organizations only when organizations
are available.
Make sure the end date exists before saving.
Use default timezone to convert input dates.