[MERGE] Adds a new builtin command 'alias' to list, set and remove bzr aliases.

[Ian Clatworthy]

Ian Clatworthy has voted approve.
Status is now: Approved
Comment:
I'll merge.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C200805302302.07075.tim%40penhey.net%3E