Meet: Language interpreters

Summary: This was created on top of D2233: Meet: Q&A queue (raise hand feature)

Test Plan: ./phpunit

Reviewers: #hkccp_developers, vanmeeuwen

Reviewed By: #hkccp_developers, vanmeeuwen

Subscribers: vanmeeuwen, #hkccp_developers

Differential Revision: https://git.kolab.org/D2245