Add bindParam to the database statement wrapper

`bindParam` allows setting the type of the bound parameter explicitly which is needed in some cases to work around incorrect casting to string done by php (i.e. https://github.com/owncloud/news/issues/457)

No changes to the public api seems to be needed since `OCP\DB::prepare` says it returns a `\Doctrine\DBAL\Statement` (maybe change that in a future PR?)

cc @DeepDiver1975 @Raydiation @karlitschek