Minor: remove quotes from around :doc:, :ref: and :method:

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-1901 users need not compute hash values for hashed shard key

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-989 additional edits
DOCS-1969: fixing organization of aggregation operators