[MERGE] show (possibly dotted) revnos in `bzr tags`, allow to sort them by time (v5)

[Aaron Bentley]

Aaron Bentley has voted approve.
Status is now: Semi-approved
Comment:
This is getting close to the point where it would make sense to factor 
the function body out into a separate function, but I think it's fine as 
is.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C20071026153811.GA16664%40chistera.yi.org%3E