[1.4.3510] Expanding a Dumping Stockpile creates a normal Stockpile

[Liinux]

I think this bug is applicable to all versions.

Steps to reproduce:
1. Create a dumping stockpile zone
2. Select the zone and click the button to expand it, use it to create a new disconnected zone
3. Notice that the newly created zone is a regular stockpile zone, and not the expected dumping stockpile zone

[Pheanox]

Thanks for the bug report, I was able to confirm this on 1.4.3510. I will get a report into the devs!