[wip] make encryption work with public gallery sharing
fix some getShareKey() and getFileKey() calls
make sure that we always use the correct user id
adapt tests to the new code
better distinction between userID and keyId
Merge branch 'master' into encryption_work_with_public_gallery

Conflicts:
	apps/files_encryption/lib/keymanager.php
	apps/files_encryption/lib/stream.php
	apps/files_encryption/lib/util.php
	apps/files_encryption/tests/crypt.php
fix getFileKey() call
Merge branch 'master' into encryption_work_with_public_gallery
fix typo in comment
Merge branch 'encryption_work_with_public_gallery' of github.com:owncloud/core into encryption_work_with_public_gallery
some small changes according to the review comments
typo fixed
Merge pull request #5976 from owncloud/encryption_work_with_public_gallery

Encryption work with public gallery