Extension:UploadWizard/CustomWikiTextLicenseFeature

This is a brief explanation of what we would like to see in a feature which fixes.

Here is a mockup (constructed by directly manipulating the page in jQuery).



User stories:
 * An experienced user is uploading a third-party image. She would like to use a license which we do not offer in the drop-down list. She is able to enter the wikitext that, when parsed, produces the license.

Other goals:
 * If possible, it would be nice to check if the wikitext (a) parses, (b) when parsed, generates at least one template which is in Category:Licenses.
 * Entering blank text should not be possible.
 * The fact that this option exists should not make it easier to skip the licensing stage without at least entering something.
 * The interface should not attract confused or just-get-it-done people to type random things.

Nongoals:
 * Offering custom licenses for own-work images. We are still going to strongly urge people to use CC-BY-SA-3.0.

Thoughts:
 * It might be useful to limit this feature to users who were autoconfirmed, or have some other user rights level that suggests they won't be confused by this, or won't abuse it.