* Adding new guides

* Replaced backend with engine

* Grammar for the encryption guide

* Grammar and Markdown style for the Transite Rewrap guide

See
https://github.com/hashicorp/engineering-docs/blob/master/writing/markdown.md
for notes on numbered Markdown lists.

* grammar and wording updates for ref arch guide

* Updating replication diagram

* Removing multi-tenant pattern guide

* Added a note 'Enterprise Only'

* Removing multi-tenant pattern guide

* Modified the topic order

* Grammar and Markdown formatting

* Grammar, Markdown syntax, and phrasing

* Grammar and Markdown syntax

* Replaced 'backend' with appropriate terms

* Added a note clarifying that replication is an enterprise-only feature

* Updated the diagram & added additional resource links

* update some grammar and ordering

* Removed the inaccurate text in index for EaaS