New methods and commands

New methods and commands

• Add a console script for generating boilerplate charts.
• Add methods for setting and resetting default timeout values.
• Add open_start_page() method.
• Add set_content(html_string) method.
• Add fill(selector, text) method.
• Add focus(selector) method.
• Fix an issue with duplicate Highcharts library declarations.
• Update an error message.
• Update translations.
• Update a Python dependency:
  -- virtualenv>=20.4.4.
• Refactor "base_case.py".

This resolves the following issues:

• #876
• #877
• #878
• #879
• #880
• #881
• #882