Disabledif JavaScript is very inefficient

Note
This patch changes javascript libraries, so be sure to purge caches and do a browser shift-reload after applying.

Performance testing:
Copy the attached bigform_test.php to the moodle root and visit with a browser.
It will be very slow to load and handle events. With the patch it's much faster.

Regression testing:
This needs to be tested on as many browsers as possible.

Some good pages to test:

• attached bigform_test.php (copy to moodle root)
  Each form group contains an Enable checkbox which enables/disables the entire group. Verify that this interacts properly with the datetime control enable boxes.
• attached samstest.php (copy to moodle root)
  In particular, verify that nested dependencies work properly:
  • In the "Disabled if things change" section:
    • Unchecking "Test checkbox" should disable the Basic and Array groups.
    • Clearing the text in the first textfield should disable the Basic and Array groups.
    • Adding text to the second textfield should disable the Basic and Array groups.
    • Changing the select to "No" should disable the Basic and Array groups.
  • In the Stacked Chain, each item disables/enables all the items below it.
  • For the Date/Duration selectors, the enable box should enable/disable the entire selector.

Other moodle pages:

• Backup UI
• XML Grade upload
• Calendar event add
• Forum settings page
• Assignment settings page