Author: Jun Pataleta
MDL-86501 form: Fix date selector calendar button mark up
* Make the calendar icon decorative.
* Mark up the calendar button accordingly:
- Render it as a `<button type="button">`
- Add label using `aria-label`.
- Use a more suitable label of "Date picker" rather than "Calendar"
- Add a `title` attribute to show a tooltip for sighted users.
- Disable/enable it accordingly by setting/removing the `disabled`
attribute.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=7a6e74a9fe57ebad017c1951fba288005213b113
http://github.com/moodle/moodle/commit/7a6e74a9fe57ebad017c1951fba288005213b113
+ 4.5 en [datepicker,core_calendar]