Fix bugs in season AJAX code

Fixes include:
- declare $wpdb as a global
- use correct variable name for response data
- fix SQL result access for multi-season add
Fix admin display bug

Ensure that accordion elements are the right size and flow correctly by
using heightStyle = "content" for the jQuery according component.
Small UI tweaks for admin

= Make the accordion wider
= Use a pointer cursor for accordion titles
Fix autocomplete for opposition

Ensure admin PHP and JS use new team_data_team class for opposition
field