Improving links in README file

Signed-off-by: Sam Kleinman <samk@10gen.com>
Remove mongodb-manual from some :program: macros

Signed-off-by: Sam Kleinman <samk@10gen.com>
Remove mongodb-manual from :program: macros

Signed-off-by: Sam Kleinman <samk@10gen.com>
Added alt attribute to image in Security Setup

Signed-off-by: Sam Kleinman <samk@10gen.com>
minor: intersphinx link correction