Core: admin notice functions now support a "type".

The type parameter is used to set a CSS class when the notices are
rendered in wp-admin. It defaults to “updated”, which is the same as
the previous behaviour, which is visually styled as the box with the
green border.

Fixes #6041

git-svn-id: https://buddypress.svn.wordpress.org/trunk@9171 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Core: render the permalink nag an error message

Previously, it’s been rendering with a green border which I think helps
make people blind to the fact that we’re asking for action to be taken
(based on real-life user testing).

See #6041

git-svn-id: https://buddypress.svn.wordpress.org/trunk@9172 cdf35c40-ae34-48e0-9cc9-0c9da1808c22