DOCS-2422: rewrite core backup doc
DOCS-2422: rewrite
DOCS-2422: clarified scope, organization, and technical details
DOCS-2422: Fix organization and scope, add tables, clarify language.
DOCS-2422: Minor fixes and adjustments
DOCS-2422: Edited the whole doc for style.
DOCS-2422: structural edits
DOCS-2422: ground up style pass
DOCS-2422: edits to structure and duplication
DOCS-2422: rewrite to be fully method centric
archiving backup draft material into draft folder