[ZEPPELIN-6075] Configuration for global Roles

[Reamer]

What is this PR for?

This PR adds global roles, which can be stored in the Zeppelin configuration.

What type of PR is it?

Feature

Todos

• [x] - Documentation

What is the Jira issue?

• https://issues.apache.org/jira/browse/ZEPPELIN-6075

How should this be tested?

• Ci

Questions:

• Does the license files need to update? No
• Is there breaking changes for older versions? No
• Does this needs documentation? Yes