Consolidate media resources into BotBuilder-Samples folder

[EricDahlvang]

Is your feature request related to a problem? Please describe. We currently have various sources for static image files: https://github.com/microsoft/BotBuilder-Samples/search?q=.jpg&unscoped_q=.jpg https://github.com/microsoft/BotBuilder-Samples/search?q=.png&unscoped_q=.png

Describe the solution you'd like If possible, static files in the samples should be a local project hosted reference, or referenced from https://github.com/microsoft/BotBuilder-Samples/tree/master/docs/media

[enhancement]