Support enabling Firebug debugging output via preference flag

[danwent]

This will make it easier for someone to "turn on debugging" when they need to troubleshoot a particular problem.

Ideally would have each of the flags support being set individually.

To start, we will probably just assume the user edits the preferences directly using about:config (though I think this would require the user to restart the browser, as we would need some way to update our cached notion of the pref values, since I assume accessing prefs very frequently would slow the browser down)

[daveschaefer]

Hey Dan, were you thinking this should write debug info to a file? To the firebug console? Have options for both?

In 2d176a8943f7a2df69034cfcc8d7db1b731924a0 and 26332676002f81914360515e1e1d25788760d28c I thought it would be useful to have a wrapper function around all of our alerts(). That way we could give the user some context on where error messages were coming from instead of anonymous popup messages. One other benefit would be we could send their output to the debug logging functions as well.

I'll grab this issue and work on it after I finish some other tasks.

[ghost]

Is this still relevant? There are some variables that control debugging output. Besides we can debug in Firefox now.