Add "MediaWiki page" property type #649
Description
Not sure yet we want this. It came up as an idea in Support User values
New "MediaWiki page" property type. With optional namespace constraint. This seems like a nice generic tool for pointing at wiki pages and could be used as poor-mans User type. We'd likely want special handling in the graph DB so like Relations it is represented as an edge connecting to the Page node rather than a property value on the Subject node. If we use the edge, than like Relations we could support property-value pairs on it, though unclear if this is useful enough to warrant the complexity both in ux and code.