Update source/faq/diagnostics.txt

Fixed improper interrogative: Why => What

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

added missing space between "database command" and "aggregate" (was run together as "database commandaggregate" as viewed in production). 

Signed-off-by: Sam Kleinman <samk@10gen.com>
copy edit of the two geo docs

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