simplify agents

[zeroXbrock]

Is your feature request related to a problem? Please describe.

Don't need to name agents; we use "admin" and "spammers" enough that we should just make those the defaults, and remove the naming interface from the user's interface.

Describe the solution you'd like

• remove “agent names” -- keep them internally so we can differentiate admin/spammers but remove the
  • it’s confusing internally and not very useful externally
  • not much obvious or practical benefit derived from agent names
  • It’s not obvious that you need to set from_pool to use agent spammers
• The default from_pool for a setup directive should be “admin”; for spam it should be “spammers” - from can still be used to override