\t in element IDs for CKEditor config UI

Problem/Motivation

The CKEditor configuration UI allows tabs to be used in toolbar group names, which is fine, but they also end up in the group's element id.
The id is only used in the configuration UI so it does not create any problems during normal use of the editor.
(Unless maybe the tab makes a difference for screen readers when moving between button groups.)

Proposed resolution

Properly replace all whitespaces using the RegExp /\s/g instead of the current use of / /g.

Remaining tasks

None

User interface changes

No visible changes.

API changes

None