title: Magento extension just for single store in multishop
body: <p>my client runs a multishop with very different products, different layouts and different domains. I developed an extension for the checkout process for one of the stores and now don't see a way to tell Magento only to work with this specific store.</p>
  
  <p>I expect this to be mentioned in the /app/etc/modules/sampleextension.xml, but didn't find any information on this in the internet.</p>
  
  <p>Is there a way to make an extension shop-specific?</p>
  
  <p>Thanks
  Thomas</p>