[Proposed Feature] improved data preparation for browser upload data

Description of Feature:

When a user uses the drag and drop uploader on the website, we should help them conform to best practices around file names and avoiding uploading litter. For example, this may be running the file names through a kabob case formatter and ignoring .DS_Store files. Additionally, we may want to auto assign mime types to the uploaded files based on the file names (see https://github.com/source-cooperative/source.coop/issues/198). The appropriate workflow might involve an intermediary screen that demonstrates what the uploaded files will be once they are uploaded, allowing users to verify the formatting that we apply. We could allow users to directly opt out of these features or simply instruct them to use direct command line access to bypass these features.

What value is this feature adding to Source Cooperative?

Help maintain best practices for users of the web uploader, which is where we would expect the majority of less experienced users to be interacting with the system.

Start at the website's drag-and-drop uploader and review issue #198 for the MIME-type context. Define the proposed intermediary preview workflow, filename formatting, litter-file handling, MIME assignment, and opt-out or command-line bypass before implementation. Done should let users verify the prepared upload and preserve the stated best practices.