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/src/util/glHelpers.js

@@ -0,0 +1,44 @@
+/*
+Utility code for our WebGL shaders
+*/
+
+/*
+Point flags - used in graph & scatter plots
+
+We want a bitmask-like flag structure, but due to webgl limitations
+must emulate it with floats.
+*/
+
+// for JS
+export const flagSelected = 1;
+export const flagNaN = 2;
+export const flagHighlight = 4;
+
+// for GLSL
+export const glPointFlags = `
+
+  const float flagSelected = 1.;
+  const float flagNaN = 2.;
+  const float flagHighlight = 4.;
+
+  bool isLowBitSet(float f) {
+    f = mod(f, 2.);
+    return (f > 0.9 && f <= 1.1);
+  }
+
+  float shiftRightOne(float f) {
+    return floor(f / 2.);
+  }
+
+  void getFlags(in float flag,
+                out bool isNaN,
+                out bool isSelected,
+                out bool isHighlight) {
+    isSelected = isLowBitSet(flag);
+    flag = shiftRightOne(flag);
+    isNaN = isLowBitSet(flag);
+    flag = shiftRightOne(flag);
+    isHighlight = isLowBitSet(flag);
+  }
+
+`;