AJAX error codes

Conflicts:
	themes/bootstrap3/js/check_save_statuses.js

- This didn't work correctly due to the way $.fn.autocomplete.ajax delays before kicking off XHR; it was not possible to return the XHR object directly for chaining .done() on the end.

Fixed the broken start index calculation when requesting records from…

Improvements to dynamic covers

- For the record, it was the Bootstrap accessibility plugin, and not Bootstrap itself, that was responsible.

Convert sources setting to an array right away and use it to determin…

Convert sources setting to an array right away and use it to determine if a source is valid so that the contents of $sourcePriority doesn't affect the check.