Add two functions for creating Python Venvs: lf-create-venv() & lf-create-activate(). These functions can used to reliably create a Python Venv containing the specified list of packages.

Currently we are using a 'user' venv that is shared. A 'user' venv is added to the Python search path and can effect any Python package, even when the user venv tools are not being directly accessed. The venv's created by lf-create-venv() only effect Python when running packages out of the venv.

The new venv's control all updates/installs to the venv in a more consistent predictable manner. Once the venv is 'activated' all python tools come from the venv (python, pip, python3,lftools.....).

Added new function lf-git-validate-jira-urls()
    # Check for JIRA URLS in the commit message

Added new function lf-check-unicode()
    # Check for JJB YAML files containing non-ascii characters. This function
    # must be run from the 'top' of the global-jjb repo

All these functions are currently unused. They have been substantially tested: https://gerrit.linuxfoundation.org/infra/c/releng/global-jjb/+/61880

These function need to be made available in a released version of global-jjb, so other developers can have access to them.