(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/ui/FieldMenus.ts

@@ -0,0 +1,17 @@
+import {menuItem, menuSubHeader} from 'app/client/ui2018/menus';
+
+interface IFieldOptions {
+  useSeparate: () => void;
+  saveAsCommon: () => void;
+  revertToCommon: () => void;
+}
+
+export function FieldSettingsMenu(useColOptions: boolean, actions: IFieldOptions) {
+  return [
+    menuSubHeader(`Using ${useColOptions ? 'common' : 'separate'} settings`),
+    useColOptions ? menuItem(actions.useSeparate, 'Use separate settings') : [
+      menuItem(actions.saveAsCommon, 'Save as common settings'),
+      menuItem(actions.revertToCommon, 'Revert to common settings'),
+    ]
+  ];
+}