Policy Plus - Semantic Policy Fragment

Over the past few days, I've been working on another aspect of the Semantic Policy System: the ability to easily produce a SPOL fragment from a policy's state. There's now a "Semantic Policy Fragment" option on the context menu of policies, which produces this dialog:

Just today, I found that there was no way to represent an empty multi-valued string in the SPOL format, so I made the None literal do that. I also saw that the value names in lists were always converted to lowercase when passed through PolFile, so I fixed that too. Finally, I added a check to PolicyProcessing that avoids a crash when Semantic Policy doesn't define all the elements in a policy.

The changes are live on GitHub.