(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/plugin/GristTable.ts

@@ -0,0 +1,38 @@
+/**
+ * Common definitions for Grist plugin APIs.
+ */
+
+/**
+ *
+ * Metadata and data for a table.  This is documenting what is currently returned by the
+ * core plugins.  Could be worth reconciling with:
+ *   https://phab.getgrist.com/w/grist_data_format/
+ * Capitalization is python-style.
+ *
+ */
+export interface GristTable {
+  table_name: string | null;  // currently allow names to be null
+  column_metadata: GristColumn[];
+  table_data: any[][];
+}
+
+export interface GristTables {
+  tables: GristTable[];
+}
+
+/**
+ *
+ * Metadata about a single column.
+ *
+ */
+export interface GristColumn {
+  id: string;
+  type: string;
+}
+
+export enum APIType {
+  ImportSourceAPI,
+  ImportProcessorAPI,
+  ParseOptionsAPI,
+  ParseFileAPI,
+}