Allow Properties to be Concepts or Basic Cards

Currently, all Properties are Descriptors by default and may not be changed. However, there are multiple potential uses for a “regular” backwards card generated from a Property, e.g., storing word forms as Properties and asking which form a particular word is in.

In terms of signifiers, a Property is underlined, has the same background as a Reference, and doesn't preview on hover. Should be simple enough to think of a way to make Properties reflect what type of Card they generate - default to italic to reflect that it's a Descriptor, add bold for Concept and remove italics for a Basic Card?