Replacing deprecated pytest code with new code

Mostly replacing deprecated pytest code with new code to prevent:
PytestDeprecationWarning: the `pytest.config` global is deprecated. Please use `request.config` or `pytest_configure` (if you're a pytest plugin) instead.

The solution involved using sb_config in place of pytest.config.option

Unrelated, there's also a small update to fix a console script used for downloading the selenium server jar file. (It's only needed when you're trying to run your own Selenium Grid)

Improve Messenger methods and a few other things

Improve Messenger methods and a few other things

• Improve methods for posting in-test messages with JS
• Update pytest-html to >= 1.20.0
• Add an example that can be run without the Pytest unittest runner (AKA pure Python)

Update pytest requirements

Update pytest requirements:

• pytest>=4.1.1
• pytest-rerunfailures>=6.0
• pytest-xdist>=1.26.0

Update console scripts and traffic-generation code

Update console scripts and traffic-generation code

• Autodetect "source" for activating virtualenv commands in bash
• Update seleniumbase console scripts menu
• Update traffic-generation code

Allow a custom timeout when waiting for link text

Allow a custom timeout for wait_for_link_text_present()
Allow a custom timeout for wait_for_link_text_visible()

Update dependencies

Update dependencies:

• pytest>=4.1.0
• pytest-cov>=2.6.1
• requests==2.20.1

Update the Selenium IDE conversion tool

• Update the Selenium IDE conversion tool
• Also update a method for clicking link text inside of dropdown menus

Update virtualenv script and manifest file

Update virtualenv script and manifest file:

• Fix echo commands in a virtualenv Windows batch file
• Update the manifest file

Simplify virtualenv installation by using shell scripts

Simplify virtualenv installation by using shell scripts

Update pytest and pytest-xdist requirements

Update pytest and pytest-xdist requirements

• pytest to 4.0.2 or greater
• pytest-xdist to 1.25.0 or greater