Media progress bar needs to be restyled to match new admin design

[melchoyce]

The current media progress bar has a 2px gap at the top, along with gradients and border radii: ​https://cloudup.com/cvsuAfM9iSo

[melchoyce]

26147.diff removes the border radii, gradients, and extra spacing on the top of the bar. However, I was unable to center the progress text.

[iammattthomas]

In 26309:

Update the media upload interfaces to match new admin design:

• Replace separate progress bar designs on media-new.php and modal media uploader with a single consistent design
• Remove side borders from list of uploads on media-new.php
• Restyle the selected photo border and checkbox on modal media uploader
• Add a Media Uploader section to color schemes with progress bar and selected photo styles

Fixes #26147. Props melchoyce, iammattthomas.

[iammattthomas]

In 26310:

Making a few more adjustments to the uploader progress bar styles. See #26147.

[iammattthomas]

In 26311:

Make sure color schemes get the 1px white border around checkboxes on the media uploader. See #26147.

[iammattthomas]

I took Mel's patch and expanded it a little bit by matching the fill color of the bar to $highlight-color in our color schemes, to inject a little bit more of the scheme customization into the UI. I've also carried the same style over to the progress bars in the modal media uploader, which previously used an entirely different style. Screenshots of the new bars are attached.

[iammattthomas]

In 26330:

Use the correct shade of blue for the default filled progress bar color, 0074a2 to match the default scheme's highlight color. See #26147.