DELETED: add_panel_parameter.html, template was no longer used, all functionality was moved to view_project_panels.html

add_visit_type.html:
- handle form errors consistent with other forms

view_project_panels.html:
- BUGFIX: errors were not showing up in the modal dialog, but in a separate page with just the JSON error message...changed CSS 'add_parameter_form' from an ID to a class since there can be more than one of them (one for each panel)
- BUGFIX: for a new panel without parameters the add parameter form would not display because it was inside the panel parameter for loop...with no parameters there was no form...rearranged the for loo and if statement to ensure that the form is always available

models.py:
- BUGFIX: project visit type allowed duplicate visit type names within a project, fixed by overriding clean similar to the subject model