Clean-up edits on User Guide.
Clean-up edits on User Guide.

* remove use of non-GitHub-accepted HTML.
* fix anchor references to use GitHub format.
* update adobe.io URLs
* replace redundant text with references

adorton-adobe/user-sync.py,adobe-apiplatform/user-sync.py,adobe-apiplatform/user-sync.py,adorton-adobe/user-sync.py