Improved capture/upload of GIF images

Added transfer history display:
- Sits in the same space the gallery image preview occupies, when not hovering over a gallery image
- Shows thumbnail, filename, and status indicator of whether the upload worked or not
- If upload didn't work, hovering over the status will display the full message for what went wrong.
- Filename links to the uploaded file on your Blombooru.
- Upload history only persists within browser session (this seemed like a good compromise)

Blombooru 1.40 implements better API key handling and adds an API endpoint we can use to read instance friendly name, version, and authentication information reliably.

Extension updated to reflect that. Now tries to read the instance information endpoint, and if successful, and instance version is above 1.40, it'll read whether the API key is required or not. If it's required, the extension settings will show an API key field and require this before uploads will function correctly.

Now works around issues with Blombooru's authentication system - API keys aren't handled correctly yet, so instead you must have a valid logon cookie for your Blombooru instance.

If an upload fails due to no authorization, the extension will now prompt you to go to your instance admin page, and log in. After that, uploads will work correctly.

New feature: 'Page Gallery'!
Click the toolbar button and you'll be shown a list of all downloadable media items on the current page. You can snipe the items you want from there, including any linked full images/videos instead of just the thumbnail.

Numerous other small tweaks and improvements.