DOCS-1431 fixing mongod/mongos typo
Doesn't convert array to set;just doesn't add dups

If dups already exist then calling $addToSet will not make the array a set -- it only affects what will happen for the add operation.
DOCS-1433, DOCS-1432: cleaning up $addToSet and $each references
Minor typo

Signed-off-by: Sam Kleinman <samk@10gen.com>
Minor typo on reference/system-collections document

Signed-off-by: Sam Kleinman <samk@10gen.com>
Another typo on administration/monitoring document

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

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

Signed-off-by: Sam Kleinman <samk@10gen.com>
Minor typo on applications.txt document

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