RadGH, Part 1 — Updated backend UI. Added new option to show cropping popup on new uploads.

[mcaskill]

From tomaszsita#49:

Hi, this is my first pull request and I haven't published anything on WordPress.org yet. So you may want to thoroughly review any changes here. Mostly cosmetic changes, and one new but rather simple feature.

Here is the new settings page, to match the WP 4.3.1 style a bit better:

Here is the new popup page. Tabs have changed to match the media uploader better:

Finally, the new feature offers a checkbox on the settings page. If enabled, we trigger the crop popup when you upload a new image through the media uploader. But it's off by default.