thunderbird-config should use new autoconfig

[jdreed]

(This is the second half of #709)

With Thunderbird 3, dropping .cfg files in /usr/lib/thunderbird-<ver> is no longer encouraged (and in fact is hard, since /usr/lib/thunderbird is versioned). We can try triggers or stupid rules hacks to make the existing method limp along, but the Right(tm) way to do is documented (in draft form) at  https://developer.mozilla.org/en/Thunderbird/Autoconfiguration

This will almost certainly require coordination with OI, as autoconfig.mit.edu is currently reserved and possibly does awesome things in our Exchange infrastructure.

[jdreed]

OI is amenable to exploring the autoconfig.mit.edu option. I'll follow up with them once I'm back from vacation.

[jdreed]

In theory, we can drop isp/mit.edu.xml into the Thunderbird install directory and it will just DTRT. We'll still have to play stupid games in the postinst because the /usr/lib subdirectory is version-specific, but *shrug*.

The XML format is documented at
 https://developer.mozilla.org/en/Thunderbird/Autoconfiguration/FileFormat/HowTo

[jdreed]

OK, this appears to work. To test it, you can enter your e-mail address in the Thunderbird account wizard as "username@…", and it will give you the correct settings. I've asked network to set up a redirect for web.mit.edu/.well-known to point to web.mit.edu/well-known (which is a locker with the config in it) and then we should be all set (basically, we should stop building thunderbird-config for anything that has Thunderbird 3.1 or higher).

[jdreed]

Network has put the redirect in place, so Thunderbird 3.1 and above will "just work" if you enter your MIT e-mail address. The downside is that for those few people who have moira list aliases, this will pick up the wrong info (whereas the old Thunderbird config used ATHENA_USER). However, standard troubleshooting techniques will reveal that their username is incorrect, and I bet they don't use Thunderbird on Athena all that often anyway. We could, in theory, do something awesome with Scripts such that the .xml file is actually script that does some cleverness with moira and hesiod, but I don't think we want or need to at this point.

So I'm going to pull thunderbird-config from the metapackages for everything except Hardy (which is blocking on #848, which hopefully I'll fix later today).

[jdreed]

This already got committed as r25153

[jdreed]

This got slightly updated in r25215-9. We apparently don't turn on backports in the squeeze build chroot, so squeeze still has icedove 3.0 (which presumably has broken autoconfig the same way thunderbird does). This is a non-issue, because it'll just mean that people who run thunderbird for the first time on squeeze will get a spurious zenity dialog saying "Please configure thunderbird manually." This is now in -dev with login-graphical 1.0