Add firefox desktop pages. Bug 975156.

Change headline for landing page. Bug 997393.
[bug 975156] Intro animation for Firefox Desktop overview page
Add customize flexible animation.
Bug 998026 - [australis] "Use instant Website ID to to make sure" in desktop/trust
Add index customize animation.
Tweaks to intro animation
Fix customize/flexible animations for RTL.
Add overview intro bg. Optimize images.
Bug 993082 - Link to localized Tom's Hardware page when available
Updates to fx desktop pages:

- Update fast/feel animation.
- Add customize icon animations.
- Factor out sync animation function.
- Fix fast section images at smaller screen sizes
- Remove sync section min-height
- Remove superfluous scale3d in customize.less
- Remove negative margin on mobile nav
- Remove leftover attr in intro-anim.html
Redirect /firefox/customize/ to fix bug 979531

Redirect to australis /firefox/desktop/customize/ page
Remove old template, less, js, images, settings, and url
Change url lookups for firefox.customize to firefox.desktop.customize
Bug 1000492 - [australis] [l10n] RTL fixes needed on australis pages
Fix bugs:

- Align hamburger icon/drop down menu
- IE 8/9 get composite sync image
- Nav menu rounded corners on mobile
- alt attributes everywhere
- Update link color in footer and on home page customize section
Merge pull request #1922 from mozilla/bug-975156-fx-desktop-pages

Bug 975156 fx desktop pages