cubicweb #1942658 add jsonp support [validation pending]

This will allow external sites to query cubicweb sites and reuse result data.

see http://en.wikipedia.org/wiki/JSONP for more details.

prioritynormal
typeenhancement
appeared in<not specified>
done in3.14.0
load0.250
load left0.000
closed by#7876:df15d194a134