Little File Explorer 4.18

- re-release only!! fix version code metadata (version code broken since v4.16) - v4.17 - Fix file cannot open when external app checks Uri permissions - Add toast notification for when file cannot be deleted - v4.16 - fix read / write grant issues on file:// uri - lower android version to 4.4 for giving out content:// uri - revert back button to ascii code for consistency - switch to sparse array to reduce memory usage