DOCS-874 changes to push operator

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-1207: fixing a broken link
DOCS-1127: additional examples of shardingState comamnd output
DOCS-1135 V8 highlight the features with exceptions

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-943 new serverStatus metrics and data
minor: rst fix
DOCS-943 minor corrections