Added a 'Assignable' boolean on Role model.

If unchecked, issues can not be assigned to users having this role.

git-svn-id: http://redmine.rubyforge.org/svn/trunk@649 e93f8b46-1217-0410-a6f0-8f06a7374b81

db/migrate/059_add_roles_assignable.rb

@@ -0,0 +1,9 @@
+class AddRolesAssignable < ActiveRecord::Migration
+  def self.up
+    add_column :roles, :assignable, :boolean, :default => true
+  end
+
+  def self.down
+    remove_column :roles, :assignable
+  end
+end