Fix for mailrestore, to avoid confusion about web- and mail-backups with same ids

- http://en.wikipedia.org/wiki/SPDY

- Directive snippets can now be made available to clients; clients can select an available directive snippet for a website - the appropriate snippet will then be written to the vhost configuration file. This is useful for example on nginx where clients have no access to the Options tab of a website.

- Make sure ISPConfig shows the correct error message (instad of an SQL error) when a website is renamed after an alias domain that still exists.
- It should be possible to create two websites with the same domain on the same server as long as the IP differs. I therefore changed the serverdomain index of the web_domain table to include the IP address.

(in incremental sql-files this was already done in upd_0064.sql)

- Enable php-fpm socket mode as default.

- Updated version number to 3.0.5.4rc1