Provide example linux build system Docker files

While we should have manylinux wheels available soon, it would be nice to provide reference Dockerfiles for common linux OSes. To begin, lets make some for Centos7, Centos8, RHEL7 and RHEL8 since these OSes, while common, are older and need updates to configure the build system to allow the Python SDK to install correctly.

If time allows, try to provide Dockerfiles for all listed, but the priority is Centos and RHEL.

Lets place all the Dockerfiles in the examples directory in the Python SDK. Each file needs a preamble stating this is not an officially support file, but a demonstration on the needed steps to configuring the appropriate build system.

Linux 'flavors':

• Centos 7
• Centos 8
• RHEL 7
• RHEL 8
• Ubuntu 16.04
• Ubuntu 18.04
• Ubuntu 20.04
• AmazonLinux2
• Debian 9
• Debian 10