Graph/scatterplot improvements (#893)

* many graph/scatterplot fixes: 722, 882, 758, 886

* fix e2e test breakage caused by graph transform work

* convert webgl point shaders to use flags rather than explicit point size

* remove unused packages from dependencies

* fix typo in regl prop name

* factor common code into util helper file

* legibility tweaks

client/__tests__/e2e/data.js

@@ -27,7 +27,7 @@ export const datasets = {
       lasso: [
         {
           "coordinates-as-percent": { x1: 0.05, y1: 0.25, x2: 0.15, y2: 0.35 },
-          count: "71"
+          count: "88"
         }
       ],
       categorical: [
@@ -92,7 +92,7 @@ export const datasets = {
       },
       lasso: {
         "coordinates-as-percent": { x1: 0.45, y1: 0.05, x2: 0.65, y2: 0.15 },
-        count: "36"
+        count: "39"
       }
     },
     scatter: {