Build: Include draggable.css and sortable.css in the CSS concat step
External: Update mousewheel plugin, copy only main file
Resizable: Remove bad workaround for draggable+resizable

This adds a compound test page for draggable+resizable, which had no coverage
before. Using that page shows that there is no way to reproduce the behaviour
described in the original ticket that caused this workaround, since its not
possible to resize an element beyond the window boundaries. Therefore removing
the workaround, which is 6+ years old and has no test coverage, seems like the
sanest approach.

Fixes #6939
Closes gh-1210
Build: Update version from pre to -pre

Ref jquery/jquery-release#61
Selectmenu: Cleanup

Ref gh-1224
Selectmenu: Don't use active items at all

Menus only use active items for nested menus which selectmenu doesn't support.
Selectmenu should only be working with focused items.

Ref gh-1224
Selectmenu: Simplify selection of focused item via keyboard

Don't go through menu to select the currently focused item.

Renamed _selectMenu() to _selectFocusedItem() for clarity.

Closes gh-1224
Selectmenu: Remove unused var
Button: Remove `ui-state-active` when disabling buttons

Fixes #9602
Closes gh-1151
Button: Whitespace
Selectmenu: Fix reference to jQuery in tests
Selectmenu: Default disabled option to null
Selectmenu: Test cleanup
Selectmenu: Test cleanup
Selectmenu: Test cleanup
Selectmenu: Test cleanup
Accordion demo: Refresh accordion after sorting
Autocomplete demo: Datasource needs min. 3 characters
Spinner tests: Remove mousewheel plugin

The plugin isn't needed nor used in the unit tests, which just trigger the
appropriate events. This works around the failure in Firefox 27/28 that we'll
try to track down separately.

Ref #9988
Button demo: Remove unnecessary anchors from popp menu