Simple time tracking functionality added. Time can be logged at issue or project level.

There's no aggregation reports for now, it's just possible to see all time entries for a project or an issue.
A new "activities" enumeration is added.
Permission for a role to log time must be set (new "Time tracking" section in role permissions screen).

git-svn-id: http://redmine.rubyforge.org/svn/trunk@368 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/issue.rb

@@ -28,7 +28,7 @@ class Issue < ActiveRecord::Base
 
   has_many :journals, :as => :journalized, :dependent => :destroy
   has_many :attachments, :as => :container, :dependent => :destroy
-
+  has_many :time_entries
   has_many :custom_values, :dependent => :delete_all, :as => :customized
   has_many :custom_fields, :through => :custom_values
 
@@ -91,6 +91,10 @@ class Issue < ActiveRecord::Base
     self.custom_values.each {|c| @custom_values_before_change.store c.custom_field_id, c.value }
     @current_journal
   end
+  
+  def spent_hours
+    @spent_hours ||= time_entries.sum(:hours) || 0
+  end
 
 private
   # Creates an history for the issue