remove obsolete console & default app options (fixes #622)

Originally I planned to remove just the console checkbox, but then I noticed there is other cruft in the code, i.e. functionality that we don't use anymore, in particular for specifying a "default app" on the b2g command line, so I removed that too. Which entrained additional code removal, like the (unused) ability to set a remote debugger client timeout in the options to *RemoteSimulatorClient.run*.

Originally I also planned to replace the checkbox with a hidden pref to enable/disable the Error Console, but then I realized that a remote toolbox connected to the "global process" will show chrome messages, including extension messages from prosthesis. So I don't think the Error Console is actually useful to anyone, not even Simulator developers, since we can connect remote tools to the global process to see these messages.

I also removed the code that displays the remote debugger port on the Dashboard if you're using Firefox 19 or older, since we only support Firefox versions from our four main distribution channels, which are currently 21-24.

There are probably some conflicts between these changes and the ones in the "toolbox per app" branch, but hopefully they are relatively minor and easy to resolve.