lua-decision: select from an empty table is not an error, let resolution go on.
domain-control: install and serve domain-control JS agent if websockets are enabled.
common: adjust mainloop notification callbacks to dominant usage patterns

Since practically none of the notification callbacks used the first
mainloop argument, it is not passed to the callbacks any more. Instead
mrp_get_*_mainloop getter functions has been added for retrieving the
mainloop pointer associated with the various objects for those few
cases where this is necessary.
common: get rid of a bunch of warnings.
murphy-db: get rid of a bunch of warnings.
lua-bindings: get rid of a bunch of warnings.
resource: get rid of a bunch of warnings.
daemon: get rid of a bunch of warnings.
domain-control: get rid of a bunch of warnings.
utils: get rid of a bunch of warnings.
common: get rid of a few more warnings.
common: fix websocklib build for older libwebsockets.