Make Snort test mechanism a fully fleshed out object

[johnwunder]

• Add Alternative_IDs: Need a place to put the Snort signature ID or other IDs that are not the STIX UUID
• Add Title: Signatures need a simple title to identify their purpose
• Add Short_Description: Can help explain the techniques used in the signature.
• Add Configurations: Need a place to put detailed configuration information for the Snort engine and processing assumptions (decoded vs. raw, etc)
• Add Keywords: Keywords are a useful construct to help with searching for or coding a file. They can also be used like custom properties while waiting for updates to the standard.

(suggested by someone who wanted to remain anonymous)