Cannot create groups with special characters

[MTRichards]

When creating users/groups in owncloud 4.5, can't create groups with any special characters (), for example, doesn't work. It allows you to create them in javascript, but then when you reload the page, they disappear - even if you assigned them to a user.

Better experience would be to allow special characters in group names. Second best would be to disallow special characters in the creation of groups.

[LukasReschke]

The reason for this is the limitation in lib/group.php:

public static function createGroup( $gid ) {
        // Check the name for bad characters
        // Allowed are: "a-z", "A-Z", "0-9" and "_.@-"
        if( preg_match( '/[^a-zA-Z0-9 _\.@\-]/', $gid )) {
            return false;
        }

This was introduced with b37fb91 by @jakobsack - it would be appreciated if someone else could check if this is needed here. If yes, we should clearly include a check in the JS.

[LukasReschke]

As I don't think it would cause any problems to allow any characters here, I removed the check.