Minor updates to Linux Agent User Guide

- Update Python version
- Update "authors" tag
- Minor edits
Updates to linux-use-root-privileges

- Update to include SSH key authentication only
- Edit for clarity
- Update "authors" tag
Minor updates to linux-catpure-image

- Minor edits based on customer feedback
Nit: clarify x509 cert format
Updates to linux-use-ssh-key

- Added and fixed screenshot in step 7 of "Create a PPK for Putty"
- Added new information about translating an openssh key to a x509 cert
for use with Azure
- Misc. edits for clarity
- Updated "authors" tag
Merge pull request #1769 from szarkos/linux-capture-image

Minor updates to linux-catpure-image
Merge pull request #1767 from szarkos/linux-agent-user-guide

Minor updates to Linux Agent User Guide
Merge pull request #1770 from szarkos/linux-use-ssh-key

Updates to linux-use-ssh-key
Fix Typo
Merge pull request #1768 from szarkos/using-root-privileges

Updates to using-root-privileges