upgrade to Firefox 20 beta 2

Conflicts:
	theme/chrome/browser/browser.css
	theme/chrome/browser/devtools/common.css
	theme/chrome/browser/devtools/layoutview.css
	theme/chrome/browser/downloads/downloads.css
	theme/chrome/browser/newtab/newTab.css
copy entire devtool dir directly from upstream (minus a bit of -moz prefix)
reverted some extra upstream changes
fixed the download icon
bumped up versions
Reverted background of the tabs toolbar
Fix 'private browsing' icon. Attempt 1 (#170)
Temp. fix for the messed up icons (#170)
Fix for the messed up icons II (#170)
Merge pull request #174 from gnome-integration-team/upgrade-to-20

Upgrade to 20