Required changes for live captions addition
Chnages enabling use of live captions
Required changes to configuration and added thrown exception
Merge branch 'IX-9.18.0' of https://github.com/kaltura/server into IX-9.17.0-PLAT-1345

Conflicts:
	alpha/lib/model/LiveEntry.php
Merge pull request #1332 from kaltura/IX-9.17.0-PLAT-1345

Ix 9.17.0 plat 1345