Mjulian/manage roundcube htaccess

Webmail module manages Roundcube htaccess.
* Max upload file size is now got from the mail module.
* Also added a default timezone to avoid Roundcube warnings
```
        Zentyal WebMail tests
                InstallNonProfilePackages: OK
                CreateVDomain: OK
                EnableModule: ERROR (success after retry)
                AddUser: OK
                LoginUser1: ERROR (success after a Apache conf symlink was fixed)
                Addressbook: OK
                AddressbookImportContact: OK
                Mail: OK
                ComposeMail: OK
                PreferencesSettings: OK
                FolderSettings: OK
                IdentitiesSettings: OK
                FiltersSettings: OK
                check-zentyal-log: OK
                check-syslog-apparmor: OK
```