Allow control of what users can view and/or clear notices
A user with minimal page privs (e.g. can just change their password, or access a few status pages or...) should not be automatically able to see notices or clear them. Because notices might contain critical system information which discloses some problem with the system, and clearing them would prevent a full firewall administrator from seeing them.
Users with priv for all pages (which includes the built-in admin) should be able to view and clear notices.
Provide 2 new privs that allow:
a) View notices (but cannot clear)
b) View and clear notices
This is a follow-on from bug #3454