(core) Speed up and upgrade build.

Summary:
- Upgrades to build-related packages:
  - Upgrade typescript, related libraries and typings.
  - Upgrade webpack, eslint; add tsc-watch, node-dev, eslint_d.

- Build organization changes:
  - Build webpack from original typescript, transpiling only; with errors still
    reported by a background tsc watching process.

- Typescript-related changes:
  - Reduce imports of AWS dependencies (very noticeable speedup)
  - Avoid auto-loading global @types
  - Client code is now built with isolatedModules flag (for safe transpilation)
  - Use allowJs to avoid copying JS files manually.

- Linting changes
  - Enhance Arcanist ESLintLinter to run before/after commands, and set up to use eslint_d
  - Update eslint config, and include .eslintignore to avoid linting generated files.
  - Include a bunch of eslint-prompted and eslint-generated fixes
  - Add no-unused-expression rule to eslint, and fix a few warnings about it

- Other items:
  - Refactor cssInput to avoid circular dependency
  - Remove a bit of unused code, libraries, dependencies

Test Plan: No behavior changes, all existing tests pass. There are 30 tests fewer reported because `test_gpath.py` was removed (it's been unused for years)

Reviewers: paulfitz

Reviewed By: paulfitz

Subscribers: paulfitz

Differential Revision: https://phab.getgrist.com/D3498

app/gen-server/lib/HomeDBManager.ts

@@ -255,10 +255,6 @@ export class HomeDBManager extends EventEmitter {
   // In restricted mode, documents should be read-only.
   private _restrictedMode: boolean = false;
 
-  public emit(event: NotifierEvent, ...args: any[]): boolean {
-    return super.emit(event, ...args);
-  }
-
   /**
    * Five aclRules, each with one group (with the names 'owners', 'editors', 'viewers',
    * 'guests', and 'members') are created by default on every new entity (Organization,
@@ -298,6 +294,10 @@ export class HomeDBManager extends EventEmitter {
     orgOnly: true
   }];
 
+  public emit(event: NotifierEvent, ...args: any[]): boolean {
+    return super.emit(event, ...args);
+  }
+
   // All groups.
   public get defaultGroups(): GroupDescriptor[] {
     return this._defaultGroups;