participants-database.php
added functionality for CSV uploads: can set matching record preferences on upload page
added better handling of multipage forms: multipage record (not signup) forms are now possible, extra notifications are not sent

CSV_Import class
added 'csv_import_value' value to the post array

PDb_Manage_Fields class
added user feedback on config save using Participants_Db::admin_message()
removed error_msgs property
value labels are now saved without slashes

PDb_Session class
added second argument to get method: default value to supply if no saved value is found

PDb_Settings class
get_identifier_columns() method is now static so it can be easily used by other classes
column titles have the column name added if there is a matching title to eliminate ambiguity

PDb_Shortcode class
$form_status value is now saved as a session value and now handled here instead of in the signup class
added set_form_status() and get_form_status() methods

PDb_Signup class
form status property is handled slightly differently to work better with multipage record forms
_send_mail() method now handles admin notification for multipage record forms
added _do_update_notify method to handle multipage record form notifications

upload_csv.php
added security code to prevent un-logged-in use
csv paramaters expanded to include match preference and match field
match preference and match field can now be set on the import page
new UI include JS to keep import mode feeback message current with setting

xnau_FormElement class
radios and checkboxes can now be groups using the "optgroup" syntax in the values array 

git-svn-id: https://plugins.svn.wordpress.org/participants-database/trunk@964403 b8457f37-d9ea-0310-8a92-e5e31aec5664