Pictures

Closes #4 (closed).

Uses BigPicture.js as an image viewer. I've looked at a lot of different image viewers, and even considered writing our own, but eventually landed on this one. It has a good API, is still supported, and fairly tiny.

Generalizes the tab navigation used in the score edit views. It's now part of common/form.html I'm strongly considering introducing this navigation across the entire site, and not just for forms, as a way to solve #120 (closed). This implementation is an experiment. lightbox.js should be included alongside this library - it provides a Bootstrap-like HTML interface for the library.

Additional changes:

• Uses Bootstrap's utility helpers to create our utilities
• All hosts allowed when in dev

Deferred features:

• Drag-and-drop file upload. This isn't crucial, and should be implemented in a way that is reusable
• AJAX image upload. I do want this, but AJAX doesn't mesh well with Django... A seperate page for uploading images works just fine for now.

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TODO:

• Deleting images - forgot about this one