Add the ability to set the User-Agent for the browser

Add the ability to set the User-Agent for the browser:

• Usage: --agent="USER-AGENT STRING"

Example:

pytest user_agent_test.py --agent="Mozilla/5.0 (Nintendo 3DS; U; ; en) Version/1.7412.EU"

Other changes:

• Fix the Docker integration
• Update console scripts for page-object manipulation
• Update several ReadMe files