(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/ExampleInfo.ts

@@ -0,0 +1,62 @@
+import {DomContents} from 'grainjs';
+
+export interface IExampleInfo {
+  id: number;
+  matcher: RegExp;
+  title: string;
+  imgUrl: string;
+  tutorialUrl: string;
+  bgColor: string;
+  desc: () => DomContents;
+  welcomeCard: WelcomeCard;
+}
+
+interface WelcomeCard {
+  title: string;
+  text: string;
+  tutorialName: string;
+}
+
+export const examples: IExampleInfo[] = [{
+  id: 1,    // Identifies the example in UserPrefs.seenExamples
+  matcher: /Lightweight CRM/,
+  title: 'Lightweight CRM',
+  imgUrl: 'https://www.getgrist.com/themes/grist/assets/images/use-cases/lightweight-crm.png',
+  tutorialUrl: 'https://support.getgrist.com/lightweight-crm/',
+  bgColor: '#FDEDD7',
+  desc: () => 'CRM template and example for linking data, and creating productive layouts.',
+  welcomeCard: {
+    title: 'Welcome to the Lightweight CRM template',
+    text: 'Check out our related tutorial for how to link data, and create ' +
+          'high-productivity layouts.',
+    tutorialName: 'Tutorial: Create a CRM',
+  },
+}, {
+  id: 2,    // Identifies the example in UserPrefs.seenExamples
+  matcher: /Investment Research/,
+  title: 'Investment Research',
+  imgUrl: 'https://www.getgrist.com/themes/grist/assets/images/use-cases/data-visualization.png',
+  tutorialUrl: 'https://support.getgrist.com/investment-research/',
+  bgColor: '#CEF2E4',
+  desc: () => 'Example for analyzing and visualizing with summary tables and linked charts.',
+  welcomeCard: {
+    title: 'Welcome to the Investment Research template',
+    text: 'Check out our related tutorial to learn how to create summary tables and charts, ' +
+          'and to link charts dynamically.',
+    tutorialName: 'Tutorial: Analyze & Visualize',
+  },
+}, {
+  id: 3,    // Identifies the example in UserPrefs.seenExamples
+  matcher: /Afterschool Program/,
+  title: 'Afterschool Program',
+  imgUrl: 'https://www.getgrist.com/themes/grist/assets/images/use-cases/business-management.png',
+  tutorialUrl: 'https://support.getgrist.com/afterschool-program/',
+  bgColor: '#D7E3F5',
+  desc: () => 'Example for how to model business data, use formulas, and manage complexity.',
+  welcomeCard: {
+    title: 'Welcome to the Afterschool Program template',
+    text: 'Check out our related tutorial for how to model business data, use formulas, ' +
+          'and manage complexity.',
+    tutorialName: 'Tutorial: Manage Business Data',
+  },
+}];