Rewrite the Gantt chart. #6276

This version of the Gantt chart supports nested charts. So Projects,
Versions, and Issues will be nested underneath their parents correctly.

Additional features:

* Move all Gantt code to Redmine::Helpers::Gantt class instead of having it in
  the Gantt class, controller, and view
* Recursive and nest sub-projects
* Recursive and nest versions
* Recursive and nest issues
* Draw a line showing when a Project is active and it's progress
* Draw a line showing when a Version is active and it's progress
* Show a version's % complete
* Change the color of Projects, Versions, and Issues if they are late or
  behind schedule
* Added Project#start_date and #due_date
* Added Project#completed_percent
* Use a mini-gravatar on the Gantt chart
* Added tests for the Gantt rendering

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@4072 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/helpers/application_helper.rb

@@ -121,6 +121,11 @@ module ApplicationHelper
 
     link_to(text, {:controller => 'repositories', :action => 'revision', :id => project, :rev => revision}, :title => l(:label_revision_id, revision))
   end
+  
+  def link_to_project(project, options={})
+    options[:class] ||= 'project'
+    link_to(h(project), {:controller => 'projects', :action => 'show', :id => project}, :class => options[:class])
+  end
 
   # Generates a link to a project if active
   # Examples:
@@ -832,6 +837,8 @@ module ApplicationHelper
         email = $1
       end
       return gravatar(email.to_s.downcase, options) unless email.blank? rescue nil
+    else
+      ''
     end
   end