hosting 6.x-0.4-alpha3

This is the third alpha for the 0.4 release of the Aegir hosting system.

• several user interface improvements.
• Added dependencies to drush make, modalframe and jquery ui
• Only a single task node is managed for each task type related to each entity. Multiple tasks are handled through node revisions.
• We now have a managed upgrade path through the 'hostmaster migrate' command.
• Primitive support for Drupal7
• Rewrote install script and documentation
• Backup performance improvements
• Backup file name changed to include the time
• One-time login link directly available in the frontend, new password reset
• Do not store passwords in settings.php for added security (it's now stored in the vhost)
• Put the site offline during migration #632984
• #595494 fix clone alias
• Reduce the number of parallel tasks to avoid killing the server under heavy task load
• API change: drop the redundant hosting_task_queue table
• Tasks have now performance measurements that tell how much time it took