[MERGE] Support for lazy registation of commands

[John Arbash Meinel]

John Arbash Meinel has voted resubmit.
Status is now: Resubmit
Comment:
Honestly, I would rather see the command layer get an overhaul so that 
we can move all core commands into being lazily loaded. I'm not 100% 
sure what we need without accessing the actual class, at a minimum I 
know we need the names. But I don't think we need options, etc. We can 
get those when we import the command and get the real object.

I, too, would rather see this as a 
"bzrlib.commands.registry.register_lazy()" rather than adding a helper 
function that basically proxies for it. (We would keep the existing 
'register_command' function in order to proxy into the registry for 
backwards compatibility.)

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C1219570986.6370.12.camel%40nemo%3E
Project: Bazaar