Some fixes and improovements for datastream uploads.
More translation.
Merge pull request #565 from willtp87/7.x.add_datastream_fix

Some fixes and improovements for datastream uploads.
better documentation
Merge pull request #567 from willtp87/7.x.add_datastream_fix

better documentation
Can have non-defined DSs again.
Stripping out duplicate extensions.
Merge pull request #568 from willtp87/7.x.add_datastream_fix

Can have non-defined DSs again.