Media: Swap in a new icon for the grid mode.

props melchoyce.
fixes #29353.

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Link to apps.wordpress.org instead of wordpress.org/mobile.

props pento.
fixes #29496.

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Media grid details: Load large images instead of originals, if available.

fixes #29498.

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i18n: Skip language chooser for localized packages.

Also fixes the install.php welcome string, which was not bring printed.

fixes #29487.

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Final about page for 4.0. Enjoy the videos!

props ryelle, melchoyce, smashcut, wonderboymusic, helen.
fixes #29494.

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Pinking shears.

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About: Make sure the images are properly responsive.

props ocean90.
see #29494.

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WordPress 4.0.

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