Added an administration setting to allow issue start date to be defaulted to blank (nil) at issue creation (#2269).

Based on the patch of #2277 contributed by Mischa The Evil.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@7733 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/controllers/issues_controller.rb

@@ -314,7 +314,7 @@ private
       render_error l(:error_no_tracker_in_project)
       return false
     end
-    @issue.start_date ||= Date.today
+    @issue.start_date ||= Date.today if Setting.default_issue_start_date_to_creation_date?
     if params[:issue].is_a?(Hash)
       @issue.safe_attributes = params[:issue]
       if User.current.allowed_to?(:add_issue_watchers, @project) && @issue.new_record?