Added a (currently unused) method to HsqlConnector that will start up
the HSQL management GUI, which is useful for debugging.
Added UncheckedUriSyntaxException.
Fixed a bug in the Liquibase code.

I can't remember where I ran into this, but the default Liquibase
ClassLoaderResourceAccessor doesn't use the context ClassLoader. That's
almost always a bad idea.
Refactored EmbeddedServer a bit.

This was part of an aborted attempt to add support for multiple webapps
to it. I could never quite get that working correctly, though, so I've
removed that functionality but left in some of the under the hood
refactoring, since I think it's an improvement.