BP-40 Audit logging for user interactions

**BP**

This is the master ticket for tracking BP-40 : Audit logging for BookieShell.

In order to make a software compliant with the security and privacy controls, we need to meet certain audit requirements.
One of them being able to track every human / user intervention in the software.
Zookeeper has something similar going on in [ZOOKEEPER-1260](https://issues.apache.org/jira/browse/ZOOKEEPER-1260).

The idea is that all user and human actions should be logged separately in a different log file which has stricter permissions and all interactions should be logged in detail.

This is useful for admins to later surmise what user interactions happened and can reconstruct the state of the system before and after the user interaction based on the audit logs.

Proposal PR - [Link](https://docs.google.com/document/d/1skocaIYC-9ZUsG7w2VAiGDbUG39ybYivrfvw9o5r2VA/edit?usp=sharing)

BP Acceptance Mail thread: [Link](http://mail-archives.apache.org/mod_mbox/bookkeeper-dev/201912.mbox/browser)