A set of tweaks to simplify electron packaging (#421)

* Replace `ormconfig.js` with a newer mechanism of configuring
    TypeORM that can be included in the source code properly.
    The path to `ormconfig.js` has always been awkward to handle,
    and eliminating the file makes building different Grist setups
    a bit simpler.
  * Remove `electron` package. It is barely used, just for some old
    remnants of an older attempt at electron packaging. It was used
    for two types, which I left at `any` for now. More code pruning is
    no doubt possible here, but I'd rather do it when Electron packaging
    has solidified.
  * Add a hook for replacing the login system, and for adding some
    extra middleware the login system may need.
  * Add support for some more possible locations of Python, which
    arise when a standalone version of it is included in the Electron
    package. This isn't very general purpose, just configurations
    that I found useful.
  * Support using grist-core within a yarn workspace - the only tweak
    needed was webpack related.
  * Allow an external ID to be optionally associated with documents.

app/server/mergedServerMain.ts

@@ -6,6 +6,7 @@
  */
 
 import {FlexServer, FlexServerOptions} from 'app/server/lib/FlexServer';
+import {GristLoginSystem} from 'app/server/lib/GristServer';
 import log from 'app/server/lib/log';
 
 // Allowed server types. We'll start one or a combination based on the value of GRIST_SERVERS
@@ -36,13 +37,14 @@ interface ServerOptions extends FlexServerOptions {
                            //    logToConsole is set to true)
   externalStorage?: boolean; // If set, documents saved to external storage such as s3 (default is to check environment
                            // variables, which get set in various ways in dev/test entry points)
+  loginSystem?: () => Promise<GristLoginSystem>;
 }
 
 /**
  * Start a server on the given port, including the functionality specified in serverTypes.
  */
 export async function main(port: number, serverTypes: ServerType[],
-                           options: ServerOptions = {logToConsole: true}) {
+                           options: ServerOptions = {}) {
   const includeHome = serverTypes.includes("home");
   const includeDocs = serverTypes.includes("docs");
   const includeStatic = serverTypes.includes("static");
@@ -50,6 +52,10 @@ export async function main(port: number, serverTypes: ServerType[],
 
   const server = new FlexServer(port, `server(${serverTypes.join(",")})`, options);
 
+  if (options.loginSystem) {
+    server.setLoginSystem(options.loginSystem);
+  }
+
   server.addCleanup();
   server.setDirectory();
 
@@ -58,7 +64,7 @@ export async function main(port: number, serverTypes: ServerType[],
     server.testAddRouter();
   }
 
-  if (options.logToConsole) { server.addLogging(); }
+  if (options.logToConsole !== false) { server.addLogging(); }
   if (options.externalStorage === false) { server.disableExternalStorage(); }
   await server.loadConfig();