(core) move client code to core

Summary:
This moves all client code to core, and makes minimal fix-ups to
get grist and grist-core to compile correctly.  The client works
in core, but I'm leaving clean-up around the build and bundles to
follow-up.

Test Plan: existing tests pass; server-dev bundle looks sane

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2627

app/client/widgets/AbstractWidget.js

@@ -0,0 +1,72 @@
+var dispose = require('../lib/dispose');
+const ko = require('knockout');
+const {fromKo} = require('grainjs');
+const ValueFormatter = require('app/common/ValueFormatter');
+
+const {cssLabel, cssRow} = require('app/client/ui/RightPanel');
+const {colorSelect} = require('app/client/ui2018/buttonSelect');
+const {testId} = require('app/client/ui2018/cssVars');
+const {cssHalfWidth, cssInlineLabel} = require('app/client/widgets/NewAbstractWidget');
+
+/**
+ * AbstractWidget - The base of the inheritance tree for widgets.
+ * @param {Function} field - The RowModel for this view field.
+ */
+function AbstractWidget(field) {
+  this.field = field;
+  this.options = field.widgetOptionsJson;
+
+  this.valueFormatter = this.autoDispose(ko.computed(() => {
+    return ValueFormatter.createFormatter(field.displayColModel().type(), this.options());
+  }));
+}
+dispose.makeDisposable(AbstractWidget);
+
+/**
+ * Builds the DOM showing configuration buttons and fields in the sidebar.
+ */
+AbstractWidget.prototype.buildConfigDom = function() {
+  throw new Error("Not Implemented");
+};
+
+/**
+ * Builds the transform prompt config DOM in the few cases where it is necessary.
+ * Child classes need not override this function if they do not require transform config options.
+ */
+AbstractWidget.prototype.buildTransformConfigDom = function() {
+  return null;
+};
+
+/**
+ * Builds the data cell DOM.
+ * @param {DataRowModel} row - The rowModel object.
+ */
+AbstractWidget.prototype.buildDom = function(row) {
+  throw new Error("Not Implemented");
+};
+
+AbstractWidget.prototype.buildColorConfigDom = function() {
+  return [
+    cssLabel('CELL COLOR'),
+    cssRow(
+      cssHalfWidth(
+        colorSelect(
+          fromKo(this.field.textColor),
+          (val) => this.field.textColor.saveOnly(val),
+          testId('text-color'),
+        ),
+        cssInlineLabel('Text')
+      ),
+      cssHalfWidth(
+        colorSelect(
+          fromKo(this.field.fillColor),
+          (val) => this.field.fillColor.saveOnly(val),
+          testId('fill-color'),
+        ),
+        cssInlineLabel('Fill')
+      )
+    )
+  ];
+};
+
+module.exports = AbstractWidget;