(core) move home server into core

Summary: This moves enough server material into core to run a home server.  The data engine is not yet incorporated (though in manual testing it works when ported).

Test Plan: existing tests pass

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2552

app/tsconfig.json

@@ -1,4 +1,5 @@
 {
+  "extends": "../buildtools/tsconfig-base.json",
   "files": [],
   "include": [],
   "references": [