improvements of select a pkpass-file

[GitHubNorb]

I discovered issues after installation from Google Play on Samsung S7:

1. Open File > Menue > the internal memory is not in the list
   Restart, than internal memory is in the list
2. The internal memory will be shown with all directories including the hidden.
   Better not show the hidden directories and files
3. Sort the list of directories and files
   I prefer sort by name. Download from TUI-fly, all files begin with 01, 02, 03...

Best regards
Norbert

Creating a issue

Thanks for your feedback - this is really important to improve the project!
Please make issues atomar and closeable. This means if you have one idea for an enhancement and experience a bug - please submit 2 issues and don't pack it all in one.
Please try to give a lot of detail - so ideally the issue can be reproduced. At the very minimum it is important to know what version of the app and what version of android you are using and where you got the app from.