Add Linksys_footer.sh, combine documentation/wiki into README.

[tomyummmm]

• Combine Documentation into README.md, remove redundant files Documentation.md and ProjectHome.md. Since almost no one looks at the documentation.md, or the wiki. Confusing for anyone trying to use this tool.
• Updated installation instructions for Ubuntu 20.04 and newer.
• Fix internal section linking
• Update README to include new Linksys_footer shell script.
• Add linksys_footer.sh to automate process of updating checksum.
• Update .gitignore.