migrate to "export default"

also, set no-use-before-define in linter

src/database.js

@@ -12,16 +12,6 @@ const shell = shellModule('database');
 
 const _clear = clear;
 
-export {
-    initialize,
-    uninitialize,
-    query,
-    transaction,
-    runInTransaction,
-    importFromFile,
-    exportToFile,
-    _clear,
-};
 
 let gConnectionPool = null;
 
@@ -170,3 +160,14 @@ async function exportToFile(file) {
     const [error] = await safe(shell.bash(cmd, {}));
     if (error) throw new BoxError(BoxError.DATABASE_ERROR, error);
 }
+
+export default {
+    initialize,
+    uninitialize,
+    query,
+    transaction,
+    runInTransaction,
+    importFromFile,
+    exportToFile,
+    _clear,
+};