Close button in group indicator should have a href attribute

[VicTachev]

Currently the close button in the group indicator does not have a href attribute. It should be included in order to meet accessibility requiremetns.

[GaloisGirl]

If it's a button, it also needs role="button", or to be rendered with the <button> tag. It's also not focusable via keyboard, nor does it have an aria-label.

The "first name" button is also wrongly rendered, and thus announced by a screen reader, as a link.

[dmanova]

As of R3 2020 the href="#" and data-role="button" properties will be added.

[dmanova]

Additional properties are needed to make it accessible and will be considered in the future.

[dmanova]

Added aria-label="Remove grouping by FIELD NAME field".