corrected errors

database/migrations/2018_07_08_193638_create_data_tables_table.php

@@ -17,7 +17,7 @@ class CreateDataTablesTable extends Migration
             $table->increments('id');
             $table->timestamps();
             $table->unsignedInteger('owner_id');
-            $table->unsignedInteger('precursor_id')->nullable(); // fork source
+            $table->unsignedInteger('parent_table_id')->nullable(); // fork source
             $table->unsignedInteger('revision'); // incremented with each applied changeset
             $table->string('title')->index(); // indexable
             $table->text('description');

database/migrations/2018_07_12_185431_create_table_comments_table.php

@@ -27,7 +27,7 @@ class CreateTableCommentsTable extends Migration
             $table->foreign('author_id')->references('id')->on('users')
                 ->onDelete('cascade');
 
-            $table->foreign('ancestor_id')->references('id')->on('comments')
+            $table->foreign('ancestor_id')->references('id')->on('table_comments')
                 ->onDelete('set null');
         });
     }