Move Rake tasks to rakelib directory

This commit moves all Rake tasks not defined in the Rakefile to a new
rakelib directory, where Rake will autodiscover and import those tasks.
Additionally, I've removed old logic in the Rakefile that manually
specified where to find and how to import those tasks.

Author: mhashizume

Rakefile

@@ -1,12 +1,9 @@
 # Rakefile for Puppet -*- ruby -*-
-RAKE_ROOT = File.dirname(__FILE__)
 
 # We need access to the Puppet.version method
 $LOAD_PATH.unshift(File.expand_path("lib"))
 require 'puppet/version'
 
-$LOAD_PATH << File.join(RAKE_ROOT, 'tasks')
-
 begin
   require 'rubygems'
   require 'rubygems/package_task'
@@ -21,8 +18,6 @@ end
 require 'rake'
 require 'open3'
 
-Dir['tasks/**/*.rake'].each { |t| load t }
-
 if Rake.application.top_level_tasks.grep(/^(pl:|package:)/).any?
   begin
     require 'packaging'