template/style for AtRisk

I wrote two wiki templates for AtRisk notes:

    {{AtRisk|num=...|short=...|text=...}}
and 
    {{AtRiskRef|num=...|short=...}}

and installed them in BLD.

"AtRisk" results in a big bright box.  "AtRiskRef" results in a small
note which links to the big bright box.  I wanted to make it clear that
BLD has three features at risk, despite having seven places in the
document where it has one or the other of these notes.  The number of
the feature, "num", has to be maintained by hand because mediawiki is
lame.

This completes ACTION-505, 'Come up with style for "At Risk" comments in
document.' 

    -- Sandro