[MERGE] Add __eq__ and __ne__ methods to Repository objects

[Robert Collins]

Robert Collins has voted tweak.
Status is now: Conditionally approved
Comment:
Seems ok, but I would expect that all repositories can be compared with
__class__ and URL.

RemoteRepository isn't using that.

I have a further question, which is - given that locks are per instance 
- is there room for bugs when containers (such as dicts or custom trees 
etc) see that a repository is 'the same' as another. In short I'm not 
100% sure that the __eq__ protocol is appropriate. (Its why I didn't do 
__eq__ initially when I taught fetch to short-circuit in that case).

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C20070806020808.GA23895%40steerpike.home.puzzling.org%3E