Adding critical to Priority field

[Rajesh K Rajaram]

I installed gnats couple of months ago and now I need to add some features
to it. I was wondering could any one of you help me in following.

1) Remove the severity field from gnats web and PR email

2) In priority I need to add critical along with High, low and medium ( I
added critical on gnatsweb.pl but when it goes through Queue-pr and file -pr
my default value is medium.)

3) When the state or responsible person is changed we get an email with link
to the PR but on submitting a new PR the receiver doesn't get a  link for
the very first time along with description, priority, etc..... How do I add
a link to the PR that is generated the very first time?

4) Adding another database to Gnats!! The documentation on gnats site
doesn't explain much about it. ( Any previous documentation if you could
refer that would be great)

Out of the above points if you guys can give me some suggestions on No:2
that will be really great. Your help on that would be highly appreciated.

Thank you so much for your time and will keep in touch

Regards
Rajesh