Add id attribute to batch form checkboxes

[pavol-tuka]

A form field element should have an id or name attribute.

https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input

[javiereguiluz]

Thanks for fixing this!

I liked your contribution a lot, but I made a small change while merging: 8fc96c6 I prefer to not use the primary key value as part of the HTML id attribute for performance reasons and to avoid potential issues with people who use non-standard values as primary keys.