OverrideValidation: Add plugin and docs

OverrideValidation: Allow in-place updates of .inf files

Adds support to the command line interface tool to perform in-place
updates of .inf files. i.e. regenerate existing overrides in the same
file.

Includes:
- microsoft#340
- microsoft#340
- microsoft#539
- microsoft#549
- microsoft#103
- microsoft#256
- microsoft#586

Co-authored-by: Bret Barkelew <bret.barkelew@microsoft.com>
Co-authored-by: Joey Vagedes <joeyvagedes@microsoft.com>
Co-authored-by: Kun Qin <kun.qin@microsoft.com>
Co-authored-by: Sean Brogan <sean.brogan@microsoft.com>
Co-authored-by: Antaeus Kleinert-Strand <antaeus.kleinertstrand@microsoft.com>
Co-authored-by: John Schock <joschock@microsoft.com>