add columns field to revision, remove index_column

app/Http/Controllers/TableController.php

@@ -51,6 +51,9 @@ class TableController extends Controller
             ]);
         }
 
+        // Now we create rows, a revision pointing to them, and the table using it.
+
+
         return "Ok.";
     }
 }

database/migrations/2018_07_08_193600_create_revisions_table.php

@@ -19,8 +19,9 @@ class CreateRevisionsTable extends Migration
             $table->unsignedInteger('refs'); // used for reference counting
             $table->unsignedInteger('ancestor_id')->index()->nullable(); // parent revision
 
-            // a column that can be used as the primary key for a table; possibly a composite column, if using a comma
+            // columns specification
-            $table->string('index_column');
+            // array with: {name, title, type}
+            $table->jsonb('columns');
 
             // author's note describing what has been changed
             $table->text('note');