Added support for additional HTTP headers to HTTP miner

[spenceation]

This change will add support for HTTP miners to add additional values to the HTTP header.

Description

This will add support for the header parameters in the HTTP miner configuration.

Motivation and Context

This will address issue #364 and expand support to applications requiring authentication with the HTTP header.

How Has This Been Tested?

This has only been tested with linting tools.

Screenshots (if appropriate)

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist

• [x ] I have updated the documentation accordingly.
• [x ] I have read the CONTRIBUTING document.
• I have added tests to cover my changes if appropriate.
• All new and existing tests passed.