Merge lp://qastaging/~bzoltan/click/vivid-transition_mirrors into lp://qastaging/ubuntu/vivid-proposed/click

Some explanation on the MR:

I have chosen to use the local ports and archive mirror because other options seems to be less optimal:

a) There is a way to measure bandwidth to/from the apt's mirror support, but that give a geographically close mirror and not a mirror with a fast access

b) Measuring the bandwidth to mirrors and trying to find the most optimal would need way much more code and would be too complex for a fairly simple problem

I decided to use a strict and limited expression to find the locally used mirror. I accept only the /XX.archive.ubuntu.com $series main/ source line. In case I do not find the mirror the code falls back to the central archive what is a safe choice.

All in all, the job here is to make the Chinese app developer's life easy. I am sure that we can make a more generic and smarter solution to support Ubuntu mirrors, but this one I believe is safe and good enough for now. Also I think it is legit idea to use the same mirror in the chroots what is used on the SDK's host environment.

Feedback and summing-up of irc discussion

Ubuntu users are suggested to use [countrycode].archive.ubuntu.com, but most users will select a random mirror server from the software center config (software-properties) or intstaller. http://i.imgur.com/2EvQIrv.png It ends up the user will not have xx.archive.ubuntu.com in /etc/apt/sources.list as reference.

It would make more sense that user can pick a mirror server during the new `click root` setup
1. A dialogue for user to pick which mirror to use. [countrycode].[ports|archive].ubuntu.com
2. The dialogue should suggest the default or preferred mirror server for the user. software-properties use user's locale to guess where is the most close mirror site.

Please note only [countrycode].[ports|archive].ubuntu.com are guarantee up-to-date, the other mirror can delay for few weeks. So we only use [countrycode].[ports|archive].ubuntu.com for phone developer.

This got merged in http://bazaar.launchpad.net/~click-hackers/click/devel/revision/555