Imgur and ImgBB support

[corbindavenport]

The older PHP-based ImageShare supported up to three different upload options, depending on the device and server configuration:

1. ImgBB "anonymous" uploads with a server-provided API key - This uploaded photos to the ImageShare ImgBB account with a two-minute automatic deletion timer.
2. ImgBB uploads with a user-provided API key - This stored photos in the user's own account, but didn't work on the Nintendo 3DS Browser and other browsers that couldn't store cookies properly.
3. Imgur anonymous uploads with a server-provided API key - This worked the best, but Imgur blocked API access to the main ImageShare server, so it only worked for other people setting up their own servers.

The new version of ImageShare (#28) switched to temporary built-in image hosting as the mechanism for sharing images and videos. This was done primarily because Imgur already cut off API access for the main server, and ImgBB starting to throttle API access on free accounts.

If there is sufficient demand, or someone is willing to do PRs, Imgur and ImgBB could be implemented again as alternative upload methods. There are a few factors to consider for alternative upload methods:

1. The upload form would have to be customized for each service. For example, ImageShare currently accepts all image and video files, but Imgur only supports a few specific video and audio formats.
2. Error handling for each service would have to be implemented, with messages displayed to the user.
3. Images should be deleted from the ImageShare server after they are uploaded to the third-party service.

Third-party hosting support adds a lot more complexity to ImageShare, which is why it was left out of the rewritten version.