EZP-21969: Added test for BinaryFileUpdateStruct
EZP-21969: Added unit test for Filesystem IO Handler
EZP-21969: Improved FilesystemTest setup
EZP-21980: Fixed IO\Handler\Filesystem::update()

Updating contents + name would update the old file's content
instead of the renamed one.
Merge pull request #626 from ezsystems/coverage/EZP-21969-IO

EZP-21969: Improve coverage in eZ/Publish/Core/IO