Seafile-1.8.0

Changes

1. support multi selection to manage downloads & uploads
2. support overwrite files being shared from other Apps
3. support sort files by name or by last modified time both in ascending and descending order
4. fixed gallery browsing progress lost error after device rotated
5. fixed searched result disappeared after device rotated
6. fixed cannot open photos error in encrypted library
7. fixed an error of ssl certificate validation
8. fix account list became empty error when upgraded to 1.7.0+