Replace mixins.less & variables.less w/lib.less. Bug 1057419.

- Delete mixins.less & variables.less.
[fix bug 1043479] Update 'Nightly User' badge link on nightly firstrun page
[fix bug 1067691] Stop redirecting Firefox Sync pages to Mozilla Taiwan website
[fix bug 1067863] Next/Prev button flicker in onboarding tour
Fix bug 1068105: page helper to skip l10n redirect based on full request path.
Merge pull request #2284 from pmclanahan/fix-page-url-util-l10n-exempt

Fix bug 1068105: page helper to skip l10n redirect based on full request path.
Revert "Revert "Add GoFox F15 phone to FxOS devices page. Bug 1065651.""

This reverts commit 8ff201e3060ca0b7707076b9475dcbd5d593d2af.

Reverts all the way down.
Bug 1064318, Bug 1067333, Bug 1066151, Add new partners for France on devices page
Fix Bug 1068413 - Change canonical, alternate, and Open Graph URLs from HTTP to HTTPS
Merge pull request #2286 from kyoshino/bug-1068413-canonical-https

Fix Bug 1068413 - Change canonical, alternate, and Open Graph URLs from HTTP to HTTPS
Merge pull request #2255 from jpetto/bug-1057419-consolidate-less-include-files

Replace mixins.less & variables.less w/lib.less. Bug 1057419.
Merge pull request #2281 from alexgibson/bug-1043479-nightly-user-badge-link

[fix bug 1043479] Update 'Nightly User' badge link on nightly firstrun page
Merge pull request #2280 from alexgibson/ui-tour-disable-button-flicker

[fix bug 1067863] Next/Prev button flicker in onboarding tour
Add FxOS GoFox F15 purchase link. Bug 1065651.

- Also add O2 to list of operators for Alcaltel One Touch Fire
  E. Bug 1068819.
Merge pull request #2288 from jpetto/bug-1065651-grameenphone-purchase-url

Add FxOS GoFox F15 purchase link. Bug 1065651.
Update GoFox F15 device name. Bug 1065651.
Merge pull request #2285 from TheoChevalier/update-french-partners

Bug 1064318, Bug 1067333, Bug 1066151, Add new partners for France on de...
Bug 1069240 - [Sync] Add extra class to display menu icon after the word
Merge pull request #2290 from flodolo/bug1069240

Bug 1069240 - [Sync] Add extra class to display menu icon after the word
[no bug] Fix broken links to coding style guides in docs