Clarify that robot query accepts multiple --query options

[allenbaron]

Requested in #1222.

• docs/ have been added/updated
• tests have been added/updated
• mvn verify says all tests pass
• mvn site says all JavaDocs correct
• CHANGELOG.md has been updated

This adds a brief comment and example, built from combining the previous two examples, to the docs for the query command to clarify that it accepts multiple --query options in a single invocation.

I also confirmed that the example works by executing it in the docs/examples dir.

How does the query command handle the --format option in this scenario. Does that need to be included in the docs as well?

[jamesaoverton]

Much appreciated!

QueryCommand iterates over the queries, handling each one separately with its own format: https://github.com/ontodev/robot/blob/master/robot-command/src/main/java/org/obolibrary/robot/QueryCommand.java#L399

The second paragraph says "The output format will be inferred from the output file extension, or you can use the --format option." so I think that's enough.