Added Event.psc_ideal_date #3411

This commit adds the attribute psc_ideal_date to Event.
The psc_ideal_date replaces the event_start_date as one of
the coupling attributes to PSC (this along with event_type).

This change also updates the PSC matching criteria to use the
psc_ideal_date attribute instead. The migrations add the column to
the database as well as update all existing records to set the psc_ideal_date
to the current event_start_date.

Additionally there is a before_save callback to set the psc_ideal_date to that
of the event_start_date if that attribute is not set.
Prevent editing event_type #3412

This commit updates the event edit form to prevent the editing
of the event_type attribute. Also this change includes the ability
to update the event_start_date without any additional steps. #3411

I have kept/added the ability to update the psc_ideal_date but this
is only for system administrators. The reason behind this is to allow
sys_admins to easily update this attribute in order to correct any
broken PSC associations.

Closes #3412
Ignore psc_ideal_date #3411

in the operational_enumerators as this is not an
MDES attribute.
Removing psc_ideal_date from view #3411

If this attribute needs to be updated we can do it on the backend.
Change migration to use execute #3411
Merge pull request #49 from NUBIC/3411_event_psc_ideal_date

3411 event psc ideal date