(core) freshen grist-core build

Summary:
 * adds a smoke test to grist-core
 * fixes a problem with highlight.js failing to load correctly
 * skips survey for default user
 * freshens docker build

Utility files in test/nbrowser are moved to core/test/nbrowser, so that gristUtils are available there. This increased the apparent size of the diff as "./" import paths needed replacing with "test/nbrowser/" paths. The utility files are untouched, except for the code to start a server - it now has a small grist-core specific conditional in it.

Test Plan: adds test

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2768

app/server/lib/FlexServer.ts

@@ -403,7 +403,12 @@ export class FlexServer implements GristServer {
         name: 'You',
         email: process.env.GRIST_DEFAULT_EMAIL,
       };
-      await this.dbManager.getUserByLoginWithRetry(profile.email, profile);
+      const user = await this.dbManager.getUserByLoginWithRetry(profile.email, profile);
+      if (user) {
+        // No need to survey this user!
+        user.isFirstTimeUser = false;
+        await user.save();
+      }
     }
     // Report which database we are using, without sensitive credentials.
     this.info.push(['database', getDatabaseUrl(this.dbManager.connection.options, false)]);

app/server/lib/NSandbox.ts

@@ -327,7 +327,9 @@ export class NSandboxCreator implements ISandboxCreator {
     // In this case, expect to find library files in a virtualenv built by core
     // buildtools/prepare_python.sh
     const pythonVersion = 'python2.7';
-    const libraryPath = `grist:../venv/lib/${pythonVersion}/site-packages`;
+    const libraryPath =
+      path.join(process.cwd(), 'sandbox', 'grist') + ':' +
+      path.join(process.cwd(), 'venv', 'lib', pythonVersion, 'site-packages');
     const args = [options.entryPoint || defaultEntryPoint];
     if (!options.entryPoint && options.comment) {
       // When using default entry point, we can add on a comment as an argument - it isn't