DOCS-1594: tutorial for restoring database into RS

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-1594: edits and refactoring
DOCS-1594: additional edits
DOCS-1927 changed language to say what the length of the key should be, not the file

Signed-off-by: Sam Kleinman <samk@10gen.com>