hosting 6.x-0.4-alpha2

Hosting is a component of the Aegir hosting system.

This is the second release of the 0.4 milestone. Many bug fixes have gone in since alpha1, plus a stack of exciting new features.

New features:

* refactor the package comparison user interface in migrate #583844: Refactor the package comparison user interface
* batch migrate of sites between platforms #587308: Batch migrate sites between platforms.

Bugfixes:
* spotted by voipfc - add missing curly brackets around tables in hosting_platform_load() #581420: Error in hosting platform_load()
* univate - replaced drupal_to_js with drupal_json #588724: Replace drupal_to_js with drupal_json
* spotted by kunago - set a default port for imported sites #588072: Ports not being set neither for imported sites nor for the aegir site
* don't render Submit button on batch migrate form if no other platforms exist, friendlier message #593758: Batch migrate form renders Submit and gives misleading form_set_error if no other platforms exist
* fix regression that prevented Clone of a site to the current platform #593880: Validation prevents clone to the current platform