Import Twitter picture and sync usernames

Issue Summary

Last weekend, I wrote a patch to extend the twitter signin module.
The patch add the following features:

1. Import user picture from twitter. At the admin page, you can configure following import settings:
- disabled,
- Once, during registration via twitter,
- Every login, unless the user chooses his own picture,
- Every login, forced copy from twitter (Hide picture settings form from user edit page).

2. Sync username on login (enable od disable at admin page):
If the given twitter name isn't used by another drupal user and the user does not have the 'change own username'-permision, the username will be updated.

This patch copy the image from twitter and doesn't any picture scaling, so I recomend to use image cache profile.

To use the features above, you have to patch twitter_signin.module and twitter_signin.pages.inc. The patch files are based on the twitter 3.0 beta 3 version.