preserve database integrity for recurring todos when deleting project or context. Fixes #880. Fixes #895

app/models/context.rb

@@ -1,6 +1,7 @@
 class Context < ActiveRecord::Base
 
   has_many :todos, :dependent => :delete_all, :include => :project, :order => "todos.completed_at DESC"
+  has_many :recurring_todos, :dependent => :delete_all
   belongs_to :user
 
   named_scope :active, :conditions => { :hide => false }

app/models/project.rb

@@ -1,6 +1,7 @@
 class Project < ActiveRecord::Base
   has_many :todos, :dependent => :delete_all, :include => :context
   has_many :notes, :dependent => :delete_all, :order => "created_at DESC"
+  has_many :recurring_todos
   belongs_to :default_context, :class_name => "Context", :foreign_key => "default_context_id"
   belongs_to :user
 

app/models/recurring_todo.rb

@@ -631,6 +631,11 @@ class RecurringTodo < ActiveRecord::Base
     end 
     starred?  
   end
+
+  def remove_from_project!
+    self.project = nil
+    self.save
+  end
   
   def inc_occurences
     self.occurences_count += 1