Improved timeline trimming, integrated Clip API calls (create, load, delete), fixed duplicate upload bug, made errors prettier / parse key/value, capitalize, and handle 404 on editor

Added multiple file uploads and progress bars. Added custom video preview controls, with trimming support and seeking support. Still a WIP.

Added file upload progress to the UI. Multiple upload progress bars are supported. Also, clicking on a file now previews the selected file. Video and images are supported.

Added real file uploading via axios, and now list actual File objects, and load project details when loading the editor. Made components conditional based on when the editor loads project data.

Removed fetch and replaced with axios (mostly due to simpler syntax, and support for upload progress events). Also added support for custom errors, for failed API calls, failed login, etc... Errors are stateful, and can be dismissed by the user.