Need "access-control-expose-headers : content-range" to make dgrid's Pagination work with JsonRest

[websoftix]

I'm testing pintura and I started from persevere-example-wiki where I'm using the MySQL store to load a list of items into a dgrid (that uses Pagination extension and dojo/store/JsonRest as store).

The visible effect is that the dgrid shows "1 - 1 of 0" in the footer and when you try to navigate to next page it will get all the products.

The headers are returned correctly by pintura but the JsonRest refuses to use content-range and gives error that is an unsafe header.

To make it work I added the following code into pintura/jsgi/rest-store.js after line 122:

if (request.crossSite) { headers["access-control-expose-headers"] = "content-range"; }

I'm not sure this is the best place to solve it, maybe it can be added in xsite.js but that's why I submited this issue before makeing a PR.