feat: update request/reponse logging, disable sanic access log

[edaniszewski]

This PR:

• disables the sanic access log, as it doesn't format messages well for structlog
• moves the existing request logging to app middleware
• adds response logging

Example logs of this new setup:

timestamp='2020-03-02T14:36:46.096092Z' logger='synse_server.app' level='debug' event='processing HTTP request' request_id='ZEXhnBYZr74w67mRgTXmxj' method='GET' ip='192.168.112.1' path='/test' headers={'host': 'localhost:5000', 'user-agent': 'curl/7.64.1', 'accept': '*/*'} args={}
timestamp='2020-03-02T14:36:46.096360Z' logger='synse_server.cmd.test' level='info' event='issuing command' request_id='ZEXhnBYZr74w67mRgTXmxj' command='TEST'
timestamp='2020-03-02T14:36:46.096907Z' logger='synse_server.app' level='debug' event='returning HTTP response' request_id='ZEXhnBYZr74w67mRgTXmxj' request='GET http://localhost:5000/test' status=200 bytes=58