register bzr url scheme

[Martin Pool]

We want to use the bzr:// url scheme, but this is not officially registered. We should register it.

[Martin Pool (mbp)]

List of schemes:

http://www.iana.org/assignments/uri-schemes.html

Guidelines and Registration Procedures for New URI Schemes (as of 2006):

http://www.rfc-editor.org/rfc/rfc4395.txt

There is an option of provisional registration, which might be appropriate or easier at this time.