cubicweb-postgis #3036205 map ST_ functions in RQL [validation pending]

ST_UNION, ST_INTERSECTION should be available in RQL.

prioritynormal
typebug
done in0.1.0
load0.100
load left0.000
closed by#db32df741824 expose ST_ function to RQL (closes #3036205)
patchRegister functions to compute convex hull of geometries. [applied][sql] Bind some postgis SQL functions in RQL [applied]expose ST_ function to RQL (closes #3036205) [folded]