[MERGE] Warn the user when resolving lp: URLs if they haven't set their login.

[Martin Pool]

Martin Pool has voted tweak.
Status is now: Semi-approved
Comment:
There should be a comma after "does".

It's not an ideal end state, because we would like anonymous users to 
get readonly access without needing to create an account, and without 
creating any impression that they must create an account.

On the other hand, I think most people using lp: urls now are in the 
Launchpad field, and many will have accounts, and certainly the 
behaviour without this is confusing.  So, please merge it.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C1205667593.7247.36.camel%40flash%3E