Move Firebug activation methods to Firebug.Module (not related to panel activation) + avoid NPE
First step towards proper backend activation + tracing (WIP)
FBTest: fix enableScriptPanel (needs to wait for async thread attach) + tracing
Modify version string so, it's easy to see it's JSD2 version
Introduce debuggerClientTab object responsible for attaching to the thread actor (and having the same life cycle as fx tab)
FBTest: yet improve enableScriptPanel