Artifact Storage

[terrorbyte]

Part of #189

This is the first pass at adding a basic artifact storage to the framework. Changes are:

• Add a SQL table for a really basic artifact set
• Add SQL for insertion and initialization
• Add exploit.StoreArtifact that will store an artifact in the output flag location and/or in the database

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Things needed before undraft:

• Add string templatizing from Config function #306 merged to add the ability to templatize output files, so we can normalize all exploit outputs
• A pass at whether the SQL tables could be improved, I already know now that the current parts I have in there are insufficient for really detailed data storage but as a "go fast" version this seems okay and solves most our cases in our real exploits.
• Another pass at docs. Making it clear that conf.SetStringFlag("output") will change behavior seems good. I honestly considered making this a "reserved" flag somehow and doing something similar to Allow for manual triggering of C2 startup #300 so that "output artifact data" becomes a config toggle explicitly. I think the magic config flag isn't ideal and could be a footgun. Another benefit of doing it Allow for manual triggering of C2 startup #300 style would be that the exploit internals could add to -details if artifact collection is expected.
• Are the flags sufficient for information? Or is it unclear what the parameters for storage are?
• Testing.
• More testing.