download with zlib streaming compression
creating a real zip file, streamed
new streaming download functions
using new download functions everywhere
version conflict fix
fix unnecessary error when there is no thumbnail
proper fix for thumbnail issues
Better buffering download
fixing tests
added directories to datasets and dataset_fieles, display of directories on dataset tiles and filtering

Conflicts:
	tardis/tardis_portal/models/datafile.py
added missing file
fixed some bugs related to tokens, permissions and added directory admin field
bug fix in authorisation