Add Boolean Search Operators to the model search functionality.

This is not what I would consider a super high priority, in fact I'm not even sure any of the other model repo sites offer it. However, the ability to use boolean search operators (OR, NOT) would be a nice addition to the search functionality. For example: If I wished to look for a screwdriver organizer but I did not want it to be for Gridfinity I could search for "screwdriver organizer NOT gridfinity". The results here would be all models that are found with the words Screwdriver Organizer, but any that have gridfinity in the title (and/or tags) would be excluded. Another example would be if I wanted to to look for a "screwdriver organizer OR holder", so it would search for all listings that are for either a Screwdriver Organizer or a Screwdriver Holder and list them.