Roundcube webmail 1.0-beta

This is a beta release of the long awaited version 1.0 of Roundcube webmail.
With this milestone we introduce some important changes to the configuration
as well as some nice new features:

• Cleaned up the configuration into a single file
• Importing email messages and contact group assignments
• Advanced LDAP address book functionality
• A toggle to switch between HTML and plaintext view
• Save drafts in local storage for recovery
• Canned responses to save and recall boilerplate texts
• Improved keyboard navigation in messages list
• Attachment reminder plugin

And of course plenty of small improvements and bug fixes.

Please note that this is a beta release and we recommend to test it on a
separate environment. And don't forget to backup your data before installing it.

WARNING: the old configuration files named main.inc.php and db.inc.php are
now deprecated and should be replaced with one single config.inc.php file.
Run the ./bin/update.sh script to get this conversion done or manually merge
the files. NOTE: the new config.inc.php should only contain options that differ
from the ones listed in defaults.inc.php