#74 Press Release - add "priority" field

[Steve Pugh]

We had a requirement from our Press Office that some
press releases should be marked with a higher priority
(i.e. "Top Story").

This field would then be used by the RSS feed generator
to show the "important" press releases at the top of
the list.

Patch is attached, however note it could be necessary
to apply our other press release patch first (#1232814)

Also note, the following SQL is required to add the
field to the database:

alter table ct_press_releases add column priority INTEGER

[Steve Pugh]

press release priority patch