Migrate README (#8621)

Docs Migration Work

### Motivation:

resolves #8595

### Modifications:

- named top-level organization file to `Documentation.md` to make it
easier to spot.
- migrate content from Documentation/README primarily into a top-level
article "Introducing Packages".
- migrated the dependency failure scenarios into it's own article
(Exploring your package's dependencies).

Author: heckj