Fixes issue #2216 [Feature Request]

"InstallShield setup.z extractor fails for Dune 2000"
Reverse engineered pascal code from "STIX", adjusted only a few line of code. 
The blast implementation of OpenRA works perfectly with it. 
Filename hashing should be removed 'cause of duplicate filenames in nested folders.

EDIT: please only merge "InstallShieldPackage.cs" I'm new to git. Maybe i'll create a concrete branch
for fixes.