Document generic replica set maintenance task

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-2230: fix step for primary member maintenance

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-2230: minor wording fixes

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-2230: Add checks and wording fixes from Asya

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-2230: minor fixes

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-2230: add new steps format

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-2230: edits