Fixes a number of issues with the image uploader. Read below,

Fixes a number of issues with the image uploader. Read below,

- Added a remove link to remove files that have an error.
- Error will appear below the progress bar.
- Hovering on dz-image or dz-details will display the error message. Otherwise error message was covering the remove link as well.
- Removed styling around the file size.
- Removed gradient effect in accordance with BookStack styling.
- Dropzone filenae will not overflow the container element. Also done for page attachments
- Added a 'uploaded' error message. this error was being thrown when the file size exceeded the server configured file size. (https://stackoverflow.com/a/42934387/903324)

Towards #741

Signed-off-by: Abijeet <redacted>