Merge pull request #3691 from ritzalam/update-screenshare-doc

bbb-screenshare/README.md

bbb-screenshare/app/jws/lib/ffmpeg-svc2.jar

bbb-screenshare/app/jws/lib/javacpp.jar

bbb-screenshare/app/jws/lib/javacv.jar

bbb-screenshare/jws/README.md

bbb-screenshare/jws/native-libs/unsigned-jars/README.md

...e/jws/native-libs/unsigned-jars/ffmpeg-3.0.2-1.2-svc2.jar

...enshare/jws/native-libs/unsigned-jars/sign-ffmpeg-svc2.sh

bbb-screenshare/jws/webstart/build.sh