This version futher enchances XMPP support, this time I have added ability to have XMPP support from GTalk just using Google APIs without requirement to enter google password.

Features

1. Now you can configure to receive an e-mail then chat is closed.
   1. First we check does mail templates has any recipients.
   2. If not then we check for department responsible users.
   3. If not we send an e-mail to admin. 
2. I have added GTalk OAuth2 support for authorisation. It allows to authorize live helper chat to send xmpp messages using OAuth logic. So you won't have to enter your password. If you are using two steps verification on google, you just have to generate application specific password if you decide to keep standard XMPP configuration, that's all.
3. Added more check for install script. mbstring and php_curl extension checks.

I will update XMPP configuration article with more detailed information how to configure XMPP and use OAuth method.

execute doc/update_db/update_48.sql for update and follow standard upgrade instructions