enabled foreign keys on startup

db/create.h

@@ -7,6 +7,7 @@
 namespace db {
   sql::Database* init(std::string name) {
     sql::Database* db = new sql::Database(name, SQLite::OPEN_READWRITE|SQLite::OPEN_CREATE);
+    db->exec("PRAGMA foreign_keys = ON;");
     DEBUG << "SQLite database file '" << db->getFilename().c_str() << "' opened successfully\n";
 
     Schema* schema = new Schema(db);