Temporary files during download/pull should go to temp directory

[wonder-sk]

Currently when doing initial download or pull, the temporary files with downloaded chunks are stored in the project's directory as filename.ext.0, filename.ext.1 etc. It would be better to keep them out of the project directory, and it may also be one of the reasons why MM plugin does not work well with OneDrive and other services (creates temp files, soon afterwards it tries to remove them while the sync service is uploading those)