Menu: Adding a demo showing how to create category headers

Closes gh-1347
Datepicker: Fix currentText in Greek locale

Thanks Nikos Kalogridis

Fixes #10620
Closes gh-1349
Menu: Filter out non-items when typing

Fixes #10571
Closes gh-1329
Menu: Maintain focus on already selected item during typeahead

Fixes #10644
Closes gh-1354
Menu: Remove a redundant check

Closes gh-1355
Menu: Typeahead now accounts for leading whitespace

Fixes #10649
Closes gh-1356
Datepicker: Fix French locale

Thanks Jérémy M

Fixes #10651
Closes gh-1357
Datepicker: Fix test for French locale

Ref #10651
Slider: Don't allow a slider's value to exceed its max

Fixes #9376
Closes gh-1016
Tooltip: Properly track hiding and closing for delegated tooltips

Fixes #10602
Closes gh-1353
Build: Update authors list
Selectmenu: Preserve text selection and button focus on click

Fixes #10639
Closes gh-1358
Build: Updating the master version to 1.11.3-pre.
Build: Update version to 1.12.0-pre
Selectmenu: When refreshing, set original tabindex