Rewrite MongoCollection::deleteIndex() documentation

https://jira.mongodb.org/browse/PHP-970

Attempted to clarify how string arguments are handled and touched up the code examples.


git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@333623 c90b9560-bf6c-de11-be94-00142212c4b1
Make see-also links consistent across MongoCollection index methods


git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@333624 c90b9560-bf6c-de11-be94-00142212c4b1