Adds subtasking (#443) including:

* priority, start/due dates, progress, estimate, spent time roll-up to parent issues
* descendant issues tree displayed on the issue view with context menu support
* issue tree display on the gantt chart
* issue tree copy on project copy
* unlimited nesting

Defining subtasks requires the new permission 'Manage subtasks'.
Subtasks can not belong to a different project than the parent task.

Implementation is based on scoped nested sets for fast reads and updates.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@3573 e93f8b46-1217-0410-a6f0-8f06a7374b81

config/locales/en.yml

@@ -112,6 +112,7 @@ en:
         greater_than_start_date: "must be greater than start date"
         not_same_project: "doesn't belong to the same project"
         circular_dependency: "This relation would create a circular dependency"
+        cant_link_an_issue_with_a_descendant: "An issue can not be linked to one of its subtasks"
 
   actionview_instancetag_blank_option: Please select
   
@@ -277,6 +278,7 @@ en:
   field_content: Content
   field_group_by: Group results by
   field_sharing: Sharing
+  field_parent_issue: Parent task
   
   setting_app_title: Application title
   setting_app_subtitle: Application subtitle
@@ -386,6 +388,7 @@ en:
   permission_delete_messages: Delete messages
   permission_delete_own_messages: Delete own messages
   permission_export_wiki_pages: Export wiki pages
+  permission_manage_subtasks: Manage subtasks
   
   project_module_issue_tracking: Issue tracking
   project_module_time_tracking: Time tracking
@@ -750,6 +753,7 @@ en:
   label_missing_api_access_key: Missing an API access key
   label_api_access_key_created_on: "API access key created {{value}} ago"
   label_profile: Profile
+  label_subtask_plural: Subtasks
   
   button_login: Login
   button_submit: Submit

config/locales/fr.yml

@@ -136,6 +136,7 @@ fr:
         greater_than_start_date: "doit être postérieure à la date de début"
         not_same_project: "n'appartient pas au même projet"
         circular_dependency: "Cette relation créerait une dépendance circulaire"
+        cant_link_an_issue_with_a_descendant: "Une demande ne peut pas être liée à l'une de ses sous-tâches"
 
   actionview_instancetag_blank_option: Choisir
   
@@ -299,6 +300,7 @@ fr:
   field_group_by: Grouper par
   field_sharing: Partage
   field_active: Actif
+  field_parent_issue: Tâche parente
   
   setting_app_title: Titre de l'application
   setting_app_subtitle: Sous-titre de l'application
@@ -408,6 +410,7 @@ fr:
   permission_delete_own_messages: Supprimer ses propres messages
   permission_export_wiki_pages: Exporter les pages
   permission_manage_project_activities: Gérer les activités
+  permission_manage_subtasks: Gérer les sous-tâches
   
   project_module_issue_tracking: Suivi des demandes
   project_module_time_tracking: Suivi du temps passé
@@ -765,6 +768,7 @@ fr:
   label_close_versions: Fermer les versions terminées
   label_revision_id: Revision {{value}}
   label_profile: Profil
+  label_subtask_pural: Sous-tâches
   
   button_login: Connexion
   button_submit: Soumettre