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 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
Bug 1054437 - Get Involved redesign
Inquiry info buttons
Moving new pages to /contribute
Consolidate templates from a common base
Form updates