DOCS-1919: document maxTimeMS

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-1919: redirects
DOCS-1919 edits
add toc refs for change-user-privileges

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-2249 redirect for change-user-privileges tutorial

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-2250: clarify read preference text
assign a user a role