Implement file download support with POST based authentication.
removed FileToken and CollectionToken, replaced by POST authentication
Get the XSRF token also via POST parameters.
Fix typo.

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Add file download via POST also to collection.
Include missing import.
addressed issue https://github.com/globaleaks/GlobaLeaks/issues/832
use by default receipt of 16 numbers fixing https://github.com/globaleaks/GlobaLeaks/issues/823
Fix conflicts in devel
addressed issue https://github.com/globaleaks/GlobaLeaks/issues/832
removed FileToken and CollectionToken, replaced by POST authentication
addressed issue https://github.com/globaleaks/GlobaLeaks/issues/832
Fix admin unittest.
Merge pull request #210 from globaleaks/fix/issues/826

Fix/issues/826