Bug 13091: Use "Tor Browser" everywhere (space included)

Changed MOZ_APP_DISPLAYNAME and brandShortName from "TorBrowser" to
"Tor Browser".
Bug 13047: Updater should not send Kernel/GTK version

Removed the %OS_VERSION% component from the update URL and replaced the
  /update/ component of the URL with /update_2/.
Added support for minSupportedOSVersion, an attribute of the <update> element
  that may be used to trigger Firefox's "unsupported platform" behavior.
  Older versions of TB will ignore this (unknown to them) attribiute.