"2020-09-28: Improve README"

[Ranzo3]

1. Change Grant to 2 statements, explicitly CREATE USER so it works even if implicit user creation is off, and to avoid creating a user with no password. Match username delphix_os

CREATE USER delphix_os@<staging_host> IDENTIFIED BY 'delphix123'
GRANT SELECT, RELOAD, REPLICATION CLIENT,REPLICATION SLAVE,SHOW VIEW, EVENT, TRIGGER on . to 'delphix_os'@'<staging_host>';

Add flush privileges;

2. Add Eliminate GRANT ALL, use least need privs

3. Specify to create delphix_os as a typical Delphix target user. Reference the docs. Specify to refresh the target and insure connectivity to delphix_os.

4. Specify to add plugin to Delphix (Reference docs), discover environment, add database, link dsource.

[arunskurian]

Updated documentation
https://delphix.github.io/mysqllinux/