Image region image does not properly support different labels

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Create a state with the image region interaction
2. Add an image to it
3. Add 1 region and give it a label with text (such as "label")
4. Try to add a response with a rule targeting that label

What is the expected output? What do you see instead?
The rule should say "is in region label" and there should be no errors. 
Instead, it says "is in region [INVALID]" and there are errors preventing 
saving the exploration (likely a validation error). If the region is named "1", 
however, everything works as expected.

Original issue reported on code.google.com by [email protected] on 31 Jul 2015 at 4:28