Fix some clippy warnings

* Rows cannot implement iterator
* DatabaseName is passed by value => Copy ?

src/lib.rs

@@ -152,6 +152,7 @@ fn path_to_cstring(p: &Path) -> Result<CString> {
 }
 
 /// Name for a database within a SQLite connection.
+#[derive(Copy,Clone)]
 pub enum DatabaseName<'a> {
     /// The main database.
     Main,