Instead of a remote check, we now check browser proxy settings against the
values specified by the tor control port.

If the control port is unavailable or broken, we send background request to
check.torproject.org and update the about:tor homepage and torbutton icon
retroactively if that fails.

As a fallback, obtain tor control password, host, port from Tor Launcher.

Add "Open Network Settings..." to Torbutton menu.

Buffering is likely eating our commands, causing us to wait forever for
responses.. Let's hope setting the buffer size and counts to 1 each will do
the trick :/.

It clears our error console, which makes debugging hard otherwise.

We'll let them tweak the Firefox prefs for this.

Offline Storage can be used as a third party tracking vector, and IndexedDB
seems impossible to clear during New Identity.

Also emit a private browsing session clearing event for good measure.

Technically, we exempt all browser-sourced content from third party auth
stripping.

Turns out some plugins handle multiple mime types.

Sometimes we seem to get a delayed plugin registration event :/.

Might as well have everything in a clean state before we even register the
plugin observer.

Also tweak the text slightly.

We made them way easier to enable with #3100. We should at least warn people
before we let them do it.

Fixes a crash issue on Windows.

Forgot to obey the spoof_english prompt, and we should use TBB defaults.

It's pretty much just a part of TBB anyways.