Support spam check plugins for new users

[lonnieezell]

We need some way to help combat spam, looking at the options out there, it seems Akismet is probably the most complete and likely most affordable for small sites.

• should have an interface so that additional plugins can be developed down the road if needed.
• should check the first 3 posts of any new user for spam. (can configure the number of posts)
• should be able to handle 3 response states:
  • success
  • spam - should be sent into moderation for review by humans
  • discard - the worst types of spam should immediately be deleted and the user banned/purged?
• should be able to disable the plugin
• be able to handle over limit responses gracefully. Would need to put the posts in for moderation if we cannot confirm it.