Implement "Snapshot" API

[smklein]

• Add API stubs
• Add to Database
• Plumb through to Crucible
• Add support in simulated sled agent / crucible
• Add integration tests in Nexus

[smklein]

Working on stubs right now

[jmpesp]

All of the tasks for this issue should be complete now, am I ok to mark them done?

[smklein]

All of the tasks for this issue should be complete now, am I ok to mark them done?

Sounds good; closing now.