Suppress "django-modern-rpc initialized" on django startup

[washeck]

modernrpc.apps loggs the number of RPC methods registered on app registration. While this can provide some debugging info, it is printed every time you run manage.py which is bit annoying and in our case even breaks autocomplete for manage.py.

I suggest to change the log level of the message to DEBUG, making it possible for users to enable it, but making it disabled by default.

[alorence]

Your suggestion seems ok. I already felt that logs produced by the library should be less verbose.