Has anyone created (or proposed) a database or clearinghouse of local and state codes, restrictions and prohibitions applicable to UAS?
So far no one has created an official database. By official I mean one that you can count on to be correct and up-to-date. There are a few people who have created databases, but they all come with the caveat that they don't guarantee the info is correct and current.
The thing is, I don't really know if you could create a reliable database with the laws the way they are. A few states have stepped in and written a preemption against local ordinances, so in those it would be fairly easy to do. But in other states there'd be no way to keep up with ordinances enacted by the the thousands of county and local governments, many of which don't maintain an easily-accessible method of publishing their laws, and most of which are written by people who know little about uas, so the laws are often very vague.
The laws are also changing quickly right now, creating an untenable situation for drone operators. The US Senate is currently considering a bill that specifically legislates against any possible fix to this situation. It's really a complete mess.
A few of the databases I have found are: