Add image to feature type options

[publicsphere]

Add image to feature type options

[smrose]

I did this, but it isn't usefully implemented as there is no means of establishing a feature value. Presumably, such values will be established with an upload, but a key remaining question is whether that upload is stored in the database itself or in the filesystem. In the latter case, there would be a directory for storing images and, to prevent clashes, a random string would be be used to name the file - that's what would be stored in the database to permit retrieval of the correct file.