Specify files manually

Changed to allow typing the file paths for the keepass database and keyfile.

Useful to open databases on cloud storage (ex `skydrive:///keepass.kdbx`<sup>1</sup>), and/or when a file is tucked away somewhere odd (like `/data/data/keepass2android.keepass2android/files/keepass.key`)


<sup>1</sup> Opening Skydrive or GoogleDrive this way is currently broken on keepass's side, other providers unknown. Filing a bug there...