started https://github.com/globaleaks/GlobaLeaks/issues/701
Merge branch 'devel' of github.com:globaleaks/GLBackend into devel
+ ZipStream from https://github.com/SpiderOak/ZipStream
implemented https://github.com/globaleaks/GlobaLeaks/issues/708
Merge branch 'devel' of github.com:globaleaks/GLBackend into devel

Conflicts:
	globaleaks/handlers/files.py