midpoint = true -> type = 'midpoint'

Makes it more consistent with entities.

js/id/behavior/draw.js

@@ -34,7 +34,7 @@ iD.behavior.Draw = function(map) {
         } else if (d.type === 'node') {
             event.clickNode(d);
 
-        } else if (d.midpoint) {
+        } else if (d.type === 'midpoint') {
             event.clickMidpoint(d);
 
         } else {

js/id/behavior/draw_way.js

@@ -17,7 +17,7 @@ iD.behavior.DrawWay = function(wayId, index, mode, baseGraph) {
     function move(datum) {
         var loc = map.mouseCoordinates();
 
-        if (datum.type === 'node' || datum.midpoint) {
+        if (datum.type === 'node' || datum.type === 'midpoint') {
             loc = datum.loc;
         } else if (datum.type === 'way') {
             loc = iD.geo.chooseIndex(datum, d3.mouse(map.surface.node()), map).loc;

js/id/renderer/map.js

@@ -92,7 +92,7 @@ iD.Map = function() {
 
             all = _.compact(_.values(only));
             filter = function(d) {
-                if (d.midpoint) {
+                if (d.type === 'midpoint') {
                     for (var i = 0; i < d.ways.length; i++) {
                         if (d.ways[i].id in only) return true;
                     }

js/id/svg/midpoints.js

@@ -20,11 +20,9 @@ iD.svg.Midpoints = function(projection) {
 
                 } else if (iD.geo.dist(projection(a.loc), projection(b.loc)) > 40) {
                     midpoints[id] = {
-                        midpoint: true,
+                        type: 'midpoint',
                         id: id,
                         loc: iD.geo.interp(a.loc, b.loc, 0.5),
-                        a: a.id,
-                        b: b.id,
                         ways: [{id: entity.id, index: j + 1}]
                     };
                 }