Replace PRODUCT_NAME with WRAPPER_NAME

This is based on the Xcode Build Setting documentation

> PRODUCT_NAME
> Description: Identifier. Specifies the name of the product the 
> target builds.
> 
> WRAPPER_NAME
> Description: Filename. Specifies the filename (including the 
> appropriate extension) of the product bundle.
Merge pull request #32 from codecaffeine/wrapper_name

Should WRAPPER_NAME replace PRODUCT_NAME during PackageApplication?