Normalized some tables. Agents and URLs are replicated tables now.

Added a clusters table for cluster centers.

Modified the dashboard queries to do running last minute aggregation.

NewEvent now computes the cluster for each event based on smallest Euclidean
distance.

Added some sample URLs for destination and referral.

Dashboard now shows cluster distribution as well.
Remove alerts and flooding.
Query optimization and only export one event per session.
Add description to the dashboard.