hrreport: Improve UX for toggling group-by options

When creating a new report based on the CiviHR Summary template, there are a number of checkboxes under "Display Options" and "Group by Options". Nothwithstanding the 6 statistic fields, one will always toggle the checkboxes in pairs. The goal of this ticket is to ensure that the user only toggles one checkbox (rather than two checkboxes).

We currently have some Javascript which tries to help this – a user may pick a checkbox under "Group by", and the corresponding checkbox under "Display" will be toggled automatically. This is a good behavior, but it's visually backward – the layout of screen strongly encourages the user to click on the checkboxes under "Display" rather than "Group by." (Note that "Display" comes before "Group by", and note that "Display" is broken down into nice headings while "Group by" has a long/unordered list.)

There are several possible ways one could resolve this. I really don't know which would be easiest, but here's a possible solution (to keep the conversation going forward):

1. Add more Javascript to go in the other direction – if the user toggles the checkbox under "Display", then automatically toggle the checkbox under "Group by." (In a sense, the toggles are bi-directional – it doesn't matter which you choose.)
2. Use CSS/JS to hide the entire "Group by" section so that the user is unaware of the double-checkbox issue.

If this problem seems challenging, then get back to us to discuss.