Adds library of Default Images

[christianhelp]

Description

• A feature that would be nice is for users to be able to add default images at their discretion

Requirements

• Adds a thumbnails section on the admin labels
• Allow for users to add and remove default images

[linear]

CK-131 Adds Default Images for each sub org

Description

• A feature that would be nice to have is a way for each sub org to have a default image assigned to it
• This would not only cut down on our blob storage but also make for a convenient way for sub orgs to not have to upload a picture of their suborg's logo each time they wish to create an event

Requirements

• Add a column to the categories table that has an option for a default picture
• This should also be added as a select option near the thumbnail. Mabe something like "upload or choose from one of the defaults" or something like that