load annotations incrementally (#1107)

* load annotations individually

* fix type check to be more general

* update node CI version from 10 to 12

* node 11

* debug print node version

* travis node version to latest

* try nvm

* remove extraneous node_js statement

* remove node version debugging printf

* incrementally load all annotations and layout

* process annotations and layout as they are loaded

* fix tests

* sort categories incrementally

* incrementally build category view summary; add category loading spinner

* add spinner to continuous metadata

* configure undoable reducer

* incremental crossfilter creation

* improve busy layout

* more layout cleanup

* correctly reconcile categories in schema

* refine layout of lsb spinners

* more spinner layout work

* more spinner layout

* always load layout before obs annotations

client/src/components/brushableHistogram/index.js

@@ -351,8 +351,8 @@ class HistogramBrush extends React.PureComponent {
     const brushX = d3
       .brushX()
       .extent([
-          [x.range()[0], y.range()[1]],
-          [x.range()[1], this.marginTop + this.height + this.marginBottom]
+        [x.range()[0], y.range()[1]],
+        [x.range()[1], this.marginTop + this.height + this.marginBottom]
       ])
       /*
       emit start so that the Undoable history can save an undo point