Logging: add trace logging with option

[matrixbot]

This issue was originally created by @kegsay at matrix-org/dendrite#898.

Add lots of nice new trace logging for debugging -- prints incoming stuff from Kafka/HTTP and outgoing responses. Print DB store/retrievals.

Add a debug level option, command line switch or whatever to activate it.

[matrixbot]

This comment was originally posted by @kegsay at matrix-org/dendrite#898 (comment).

matrix-org/dendrite#898 does HTTP
Can maybe use https://github.com/ngrok/sqlmw for database stuff. Need to think about naffka/kafka stuff.

[matrixbot]

This comment was originally posted by @kegsay at matrix-org/dendrite#898 (comment).

This was done when matrix-org/dendrite#968 landed