[bug 884933] redirect mobile platforms page url to sumo
Update image helpers to work in tandem. Bug 911255.

- Add l10n param to platform_img & high_res_img.

- Refactor img_l10n -> l10n_img.

- Update coding docs.
Bug 931081 - [SEO] Add meta robots noindex to in-product or embedded pages
Merge pull request #1300 from alexgibson/bug-884933-fix-redirect-for-mobile-platforms-page

[bug 884933] fix redirect mobile platforms page to SUMO
Merge pull request #1270 from jpetto/bug-911255-chainable-image-helpers

Update image helpers to work in tandem. Bug 911255.
Merge pull request #1344 from kyoshino/bug-931081-noindex

Bug 931081 - [SEO] Add meta robots noindex to in-product or embedded pages