Also fixed invalid links in tokens. Now that the tokens are only URLs,
it never makes sense to show the 'Download link not available' text.
Instead, tokens could contain the custom webform token suffix of :clear
to ensure the path is cleared from output when the link is not
available.

* Use webform's own settings for the default allowed extensions.
* Update allowed extensions with AJAX rather than requiring the handler
  to be saved before uploading a file with a newly-allowed extension.
* Also fixed tokens not being replaced in upload directory location.

Also removed unused custom entity storage handler.

Token should only include the URL so it works within non-HTML contexts
like emails. HTML contexts can simply use the token in an href attribute
of an anchor tag.

Moved saving the protected download entity back to an implementation of
`hook_webform_submission_insert()`, because the entity needs creating
before any tokens would be replaced, such as for email handlers which
may be invoked before our own handler.

- Supports multiple files by using one handler per file.
- Updated Readme with some basic instructions for use.
- Improved performance when many downloads have been configured (as now
  using filterable entity queries rather than only filtering after
  loading every single protected download entity).
- Fixed compatibility with generating tokens in different ways.

Module Code changes, code impovements

Module improvements

Issue #5 - Changed permission for route webform_protected_downloads.settings so now only webform admins can access this page

Issue #6 - Changed status of file to TRUE in form submit, so  when cron runs file doesn' t get deleted.