Normalize Readmes

[mikehoffms]

This PR makes the following changes:

• Adds missing Readmes for individual samples or for intermediate directory levels.
• Removes content from Readmes so that Readmes contain only a few items:
  • Which version of Visual Studio was used. Which coding languages are used.
  • Link to regular docs at DMC. See rendered PR 2069 for latest design of detailed destination pages.
  • Screenshot of running sample app.

To view & navigate among the rendered readmes:
Files Changed tab > scroll to any Readme file > ... > View File.
Then, you can click the breadcrumb path at top, or click another Readme file at any level of the dir structure. Keep an eye on the commit ID in the URL.