Refactor CSS and React logic for layout (#1424)

* Refactor CSS layout and react logic for layout

Fixes https://github.com/chanzuckerberg/cellxgene/issues/1022

* Menubar should wrap inside middle pane instead of overlapping left
  sidebar when window is scrunched
* cellxgene should have a minimum width of 1240px

1. Replace absolute positioning and dimension calculation with css grid
2. Use flexbox for wrapping menubar buttons

* Middle pane (graph) can calculate its own size
* Removing components calculating their size/position relative to
  eachother increases modularity, decreases use of global variables
* Improved some scrollbar behavior
* Removed responsive reducer, propagating window size to components
  triggers unnecessary events and encourages breaking modularity; doing
  this made some components state agnostic

Reference: https://css-tricks.com/snippets/css/complete-guide-grid/

* Reposition the continuous legend

* Small fixes

* Respond to feedback from @colinmegill

* Respond to feedback from @colinmegill

Add more documentation on the renderGraph method.

client/src/components/termsPrompt/index.js

@@ -9,6 +9,7 @@ import {
   Icon,
 } from "@blueprintjs/core";
 import * as globals from "../../globals";
+import { termsOfServiceToast } from "../framework/toasters";
 
 const CookieDecision = "cxg.cookieDecision";
 
@@ -25,9 +26,7 @@ function storageGet(key, defaultValue = null) {
 function storageSet(key, value) {
   try {
     window.localStorage.setItem(key, value);
-  } catch {
-    return;
-  }
+  } catch {}
 }
 
 @connect((state) => ({