Merge branch 'landing/4026' into upstream-master

Land rapid7#4026

* db.rb (DBManager) now in multiple files
* Cucumber coverage for DB-related msfconsole commands

Author: trevrosen

lib/msf/core/database_event.rb

@@ -0,0 +1,34 @@
+# Events that can occur in the host/service database.
+module Msf::DatabaseEvent
+  # Called when a new client is added to the database.  The client
+  # parameter is of type Client.
+  def on_db_client(client)
+  end
+
+  # Called when a new host is added to the database.  The host parameter is
+  # of type Host.
+  def on_db_host(host)
+  end
+
+  # Called when an existing host's state changes
+  def on_db_host_state(host, ostate)
+  end
+
+  # Called when a new reference is created.
+  def on_db_ref(ref)
+  end
+
+  # Called when a new service is added to the database.  The service
+  # parameter is of type Service.
+  def on_db_service(service)
+  end
+
+  # Called when an existing service's state changes
+  def on_db_service_state(host, port, ostate)
+  end
+
+  # Called when an applicable vulnerability is found for a service.  The vuln
+  # parameter is of type Vuln.
+  def on_db_vuln(vuln)
+  end
+end