Changed MSG signature slightly
Moved restart_me from callback function to MSG

DRY with CommonMessageHandler

Conflicts:
	addon/lib/adb/adb-server-thread.js
Moved getLastError to JsMessage
Ported web-worker spawning to JsMessage

Conflicts:
	addon/lib/adb/adb-server-thread.js
Return -1 on unknown message and catch all errors
Fixed rebase conflicts