imporved handling of browsers waiting for events to be projected
* EventSourceServer is now a singleton threadsafe class that manages waiting SSE responses for projections
* using find_or_create with reasonable database defaults
* improved names
* added a fully cached_projection_repository
* changed the distribution of projections to servers
* projection_type_registry no longer contains application logic
* fixed a naming error for generating _projection.rb and the actual class name inside