Add an option to force a redirect to the mobile client when joining

[mconf-daileon]

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Author Name: Leonardo Daronco (Leonardo Daronco)
Original Redmine Issue: 1533, http://dev.mconf.org/redmine/issues/1533
Original Date: 2015-03-30

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There is already an option to force the redirect to the desktop client, but it would also be good to have an option to force the redirect to the mobile client. Can be used as a temporary fix when the user-agent is not detected as a mobile device.