Add Python script and update VSIX generator rules to pre-generate the Atmel Studio cache files required to make the extension visible.

LUFA/StudioIntegration/VSIX/[Content_Types].xml

@@ -1,5 +1,6 @@
 <Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">
   <Default Extension="vsixmanifest" ContentType="text/xml"/>
+  <Default Extension="cache" ContentType="text/xml"/>
   <Default Extension="png" ContentType="application/octet-stream"/>
   <Default Extension="txt" ContentType="text/plain"/>
   <Default Extension="xml" ContentType="text/xml"/>