DOCS-156 move block-level / snapshot backup to tutorials
DOCS-156 move binary database dumps to tutorials
DOCS-156 sharded clusters and replica sets
DOCS-156 fixing links
DOCS-156 edits to overview page
DOCS-156 edits to block-level/snapshots tutorial
DOCS-156 edits to binary database dumps tutorial
merge: DOCS-156
DOCS-156 editing and integration