Allow the minimum Elasticearch query size to be set per endpoint

Reverse queries don't need as much deduping, for example

middleware/sizeCalculator.js

@@ -9,6 +9,10 @@ var MIN_QUERY_SIZE = 20;
  * incorporating padding for dedupe process
  */
 function setup(min_size) {
+  if (min_size === undefined) {
+    min_size = MIN_QUERY_SIZE;
+  }
+
   return function setQuerySize(req, res, next) {
     if (_.isUndefined(req.clean) || _.isUndefined(req.clean.size)) {
       return next();
@@ -25,8 +29,8 @@ function setup(min_size) {
  * @param {number} cleanSize
  * @returns {number}
  */
-function calculateSize(cleanSize) {
-  return Math.max(MIN_QUERY_SIZE, cleanSize * SIZE_PADDING);
+function calculateSize(cleanSize, min_size) {
+  return Math.max(min_size, cleanSize * SIZE_PADDING);
 }
 
 module.exports = setup;