Fixes echo problem with native simulcast when the local participant is selected.
Minor simulcast code cleanup.
Renames simulcast related classes.
Splits the simulcast management in two parts, a receiver and a sender.

Splits the simulcast management in two classes, a SimulcastReceiver and a SimulcastSender. A SimulcastManager class manages the receiver and the sender. The SimulcastSender class specializes into the NativeSimulcastSender, SimpleSimulcastSender and NoSimulcastSender classes.
Attempts to prevent blackness when switching simulcast streams.
Fixes error when simulcast is disabled.
Removes usr/share/doc/ from debian folder. Fixes build.
Reverts 774785 "Attempts to prevent blackness when switching simulcast streams."

It seems to break things when testing with multiple tabs open.
Fixes the issues with resolution value when simulcast is enabled.
Don't reference simulcastUtils of parent.
Reverts 774785 "Attempts to prevent blackness when switching simulcast streams."

It seems to break things when testing with multiple tabs open.
Implements API that allows external applications to embed Jitsi Meet.
Change the css theme of the chat.