bueditor 6.x-2.7

Changes since 6.x-2.6:

- #1505324: Made the popup close button a real button element with a title.
- #1505324: Add label elements to popup forms and add a descriptive title to the required fields.
- #1505324: Added dialog role for the popups.
- #1547292: Check icon sizes besides icon names to create the unique sprite name.
- #1259978: Fixed dialog crash on zoom
- #1831984: Now using setSelectionRange detection for browser mode
- Removed late initiation as it won't work as expected when the script is loaded dynamically.
- Fixed missing length in autocomplete pair removal.
- Fixed colspan in available editors table.