Added support for animal participants and samples

This will be accessible through menu.psp in a future commit
Modify SP to deal with animal participants
Add SP and function to add animal participants
Modify field names to match form field IDs
Add page used by AJAX to check participant name

Returns an error message if the value in form['participant_name'] already
exists.
Add support for animal participants

Menu now shows animal participants, similar to human participants
More changes to ag_animal_surey table in DB to match with psp form
Add a "comments" text box to the survey, change some form field names/IDs
Rename icon
Add animal participants to main menu