Currently the process of adding a custom image to badge is quite clunky; you have to upload your image to a topic, and then copy the image URL and pasting it in a text field. Besides being clucky, if the topic or post that contains the image is deleted, the image will be garbage-collected in a few days and the badge will lose the image because the application is not that the image is referenced by a badge.
This commit improves that by adding a proper image uploader widget for badge images.
Being that system badges ship with every instance of Discourse, we've opted to define the name, description, and long description in our locales files to promote translation into other languages. When an admin visited the overview page of a system badge in their admin panel, they were met with disabled inputs for these text properties. The problem is that we failed to educate the admin that the text needs to be managed via the site text customization settings.
This change adds a small "Customize Text" link under theses inputs that takes the admin to the specific site text customization where they can make desired changes.
