Add BrowserID authentication support

[François Marier]

It would be great to use BrowserID for two things:

- password-less authentication
- automatic verification of email addresses

https://github.com/mozilla/browserid/wiki/How-to-Use-BrowserID-on-Your-Site

A simple demo of how this works in PHP:

  https://github.com/fmarier/browserid-phpdemo

[François Marier (fmarier)]

http://gitorious.org/~fmarier/mahara/francois-sandbox/commits/bug894211

[François Marier (fmarier)]

https://reviews.mahara.org/#change,938

[Mahara Bot (dev-mahara)]

Reviewed: https://reviews.mahara.org/938
Committed: http://gitorious.org/mahara/mahara/commit/f14c383edfbc3ed0e821a3d93f53e74caf6679f5
Submitter: Richard Mansfield (<email address hidden>)
Branch: master

commit f14c383edfbc3ed0e821a3d93f53e74caf6679f5
Author: Francois Marier <email address hidden>
Date: Fri Dec 9 15:53:57 2011 +1300

    New BrowserID auth plugin (bug #894211)

    Existing users can now login through BrowserID using one of their
    confirmed email addresses as long as one of the institutions they
    belong to has enabled BrowserID. We are ignoring the auth
    instance that these user accounts are tied to.

    Automatic creation of accounts is enabled. The only outstanding
    issue is to figure out what authinstance we should use for
    creating accounts. However that's a general problem with the
    authentication system in Mahara, it's not specific to this
    plugin. Currently, we make sure that it is an institution that:

    - has registrations enabled
    - is not full

    When an account is automatically provisioned, the username
    is set to the user's email address since that's the only piece
    of information we can reliably get from BrowserID.

    Change-Id: I12e59271449654d2bb394511d5ce5adfb081aa11
    Signed-off-by: Francois Marier <email address hidden>

[Melissa Draper (melissa)]

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