changing method for getting profile types by path as suggested in http://drupal.org/node/1577650. this also affects method for dealing with AJAX requests. possibly much better approach.

changing approach for determining paths. removing all uses of arg() in favor of menu_get_item(). This is an attempt to mitigate issues mentioned in http://drupal.org/node/1431286

broken out field attaching functionality in to separate function to accomodate future implementation of profile2_regpath_blocks, which will need to share the new function.