Nested file path creation, before upload to Zync

Hey,

Ultimately it may be better for the client app to gain enough smarts to deal with this case instead. **This is code which could probably do with proper testing/work on it too.**

For renders where a nested file output path is specified in the render globals the frames do not currently get downloaded back to us. The rsync fails when it can't access the parent folder for frame it wants to transfer. This commit creates those folders shortly before submitting the job into zync.

For example, for the output path:

    zync_test/v001/<RenderLayer>/1920x1080/CR_001_zync_test-<RenderLayer>-<RenderPass>_v001

the file path:

    ${ZYNC_OUT_PATH}/zync_test/v001/masterLayer/1920x1080/

would be created.