Privacy form spam prevention. Bug 865853.

- Added general use CSRF failure view.

- Added CSRF & honeypot to /privacy form.

- Added legend to global headings CSS selector.

- Added legend to global h5 CSS selector.
Merge pull request #878 from mozilla/bug-865853-privacy-spam-prevention
[Fix Bug 748503] Rewrite for Nightly Redesign
Merge pull request #890 from Sancus/master
Enable GA tracking on new /firstrun/b5/ URL. Bug 873899.
Fix Bug 589067, remove browser version detection and display from ui and perfedies
Bug 772952 - Security error when searching using Tabzilla
Merge pull request #900 from kyoshino/bug-772952-mixed-content

Bug 772952 - Security error when searching using Tabzilla
Bug 866644 - Update www.mozilla.org/book to contain the latest Book of Mozilla verse.
Bug 874903: Update Tabzilla to CDN URLs.

Also fix styleguide Tabzilla docs.
Port localized versions of Manifesto to Bedrock
Bug 869489
Merge pull request #894 from sgarrity/bug-869489-manifesto-l10n

Bug 869489 - Port localized versions of Manifesto to Bedrock
Merge pull request #903 from pmclanahan/update-tabzilla-urls-bug-874903
Merge pull request #899 from ossreleasefeed/bug589067-remove-browser-version-from-ui
Merge pull request #901 from gerv/master

Bug 866644 - Update www.mozilla.org/book to contain the latest Book of Mozilla verse
/media to /static conversion