Make AR a soft dependency again

Ensures that the absence of activerecord does not prevent msfconsole
from loading. This returns us to the previous state of affairs where it
is possible to use the framework entirely without a database.

To test:
  1. rm -rf lib/gemcache/ruby/1.9.1/gems/activerecord*
  2. remove any locally installed versions of activerecord
  3. msfconsole

msfconsole should load up with a warning like so:

[-] ***
[-] * WARNING: No database support: LoadError cannot load such file -- active_record
[-] ***

... and should still be functional.

lib/msf/core/db_manager.rb

@@ -1,5 +1,4 @@
 # -*- coding: binary -*-
-require "active_record"
 
 require 'msf/core'
 require 'msf/core/db'
@@ -7,14 +6,6 @@ require 'msf/core/task_manager'
 require 'fileutils'
 require 'shellwords'
 
-# Provide access to ActiveRecord models shared w/ commercial versions
-require "metasploit_data_models"
-
-# Patches issues with ActiveRecord
-require "msf/core/patches/active_record"
-
-
-
 module Msf
 
 ###
@@ -36,16 +27,6 @@ class DBManager
 		end
 	end
 
-	# Only include Mdm if we're not using Metasploit commercial versions
-	# If Mdm::Host is defined, the dynamically created classes
-	# are already in the object space
-	begin
-    include MetasploitDataModels unless defined? Mdm::Host
-	rescue NameError => e
-	warn_about_rubies
-	raise e
-	end
-
 	# Provides :framework and other accessors
 	include Framework::Offspring
 
@@ -117,6 +98,14 @@ class DBManager
 			# Database drivers can reset our KCODE, do not let them
 			$KCODE = 'NONE' if RUBY_VERSION =~ /^1\.8\./
 
+			require "active_record"
+
+			# Provide access to ActiveRecord models shared w/ commercial versions
+			require "metasploit_data_models"
+
+			# Patches issues with ActiveRecord
+			require "msf/core/patches/active_record"
+
 			@usable = true
 
 		rescue ::Exception => e
@@ -125,6 +114,16 @@ class DBManager
 			return false
 		end
 
+		# Only include Mdm if we're not using Metasploit commercial versions
+		# If Mdm::Host is defined, the dynamically created classes
+		# are already in the object space
+		begin
+			include MetasploitDataModels unless defined? Mdm::Host
+		rescue NameError => e
+			warn_about_rubies
+			raise e
+		end
+
 		#
 		# Determine what drivers are available
 		#