Move connections and script injection to protocol

Move connection management from LiveDocument to LiveDevProtocol:
- clients is now an optional parameter to invoke remote calls. If it
isn't present protocol will broadcast messages to all active clients.
- Connection.[connect|close] events are triggered for each new and
closed connection.

Move remote script injection from LiveDocument.onConnect to
getRemoteScripts.
- It avoids side effects when injected scripts are evaluated after
the page is loaded
Merge branch 'connections-u' into connections-d

Conflicts:
	LiveDevelopment.js
	protocol/LiveDevProtocol.js