Update track_control_helper.rb

fix the duplicated option occurred when editing an existing issue.
Update _form.html.erb

add the maxlenght for the subject input. make it consistent with redmine2.3.3
Update _form.html.erb

Reload the form if the default tracker_id was filtered by permission control.
Merge pull request #19 from samhe/redmine2

Reload the form when the default tracker id is filtered by permission setting