Documentation and type improvements

1. Update docker image example as in https://github.com/confluentinc/confluent-kafka-javascript/issues/48.
2. Improve documentation, examples, and types around the callbacks we permit to use through configuration as in https://github.com/confluentinc/confluent-kafka-javascript/issues/118 and https://github.com/confluentinc/confluent-kafka-javascript/issues/65 .
3. Update instructions on how to install on system with no pre-built binaries as in https://github.com/confluentinc/confluent-kafka-javascript/issues/10 - DONE within introduction
4. Check and update any logger examples as in https://github.com/confluentinc/confluent-kafka-javascript/issues/41 - DONE within introduction
5. Instructions for using GSSAPI (needs librdkafka build)