Allow modifying the sequence of variables displayed for a site

[mbarneytu]

On a site's page on MMW, it would be great to be able to re-order the variables on the display. Right now the only way I know of to do this is to re-create the site from scratch and with the variables entered in the desired order. My use case is an existing site that reports temperature in degrees C, we want to also display degrees F, but to have the two variables display side-by-side.