Progressbar: replace image reference in base CSS with data URI

The CSS for the Progressbar widget contained a reference to
"images/animated-overlay.gif", which is not included in custom jQuery UI
builds with "no theme" selected. This replaces the reference with a data URI.

Fixes #10134
Closes gh-1276
Theme: Add support comments for filter properties
Dialog demo: Remove a duplicate (and incorrect) script include
Spinner: Fix inclusion of mousewheel plugin in demos

Fixes #10188
Datepicker: reject dates with two year digits when expecting 'yy'

Fixes #8353
Closes gh-1248
Datepicker: Set explicit button text in demo

Fixes #9626
Closes gh-1283
Effect: Create a local jQuery variable to make jQuery Color work

Fixes #10199
Closes gh-1282
Draggable: Only apply ui-draggable-handle within the draggable instance

Fixes #10212
Closes gh-1284
Draggable: Manage ui-draggable-handle correctly in nested instances
Datepicker: Show year/month on the same line

Fixes #7953
Closes gh-1277
Tabs: Work around bad Safari/VoiceOver heuristics

Move disabled tab click handlers from the container to the tablist to
prevent panel contents from being announced as clickable.

Fixes #10098
Closes gh-1261
Resizable: Remove accidental exposure of internal data in events

Fixes #10148
Closes gh-1279
Dialog: Fix stacking of modal dialog overlays

Fixes #10138
Closes gh-1286
Build: Upgrade to jquery-mousewheel 3.1.12
Dialog: Track the instance as soon as the dialog is opened

Fixes #10152
Datepicker: Abstract mouseover logic to avoid explicit event trigger

The reliance on `.mouseover()` caused an issue in some circumstances
(see #5816). The removal of `.mouseover()` broke keyboard navigation
(see #10319).

Fixes #10319
Closes gh-1290
Widget: Improve performance of cleanData method

Fixes #9546
Closes gh-1291
Position: Support positioning within document with jQuery 1.6.x

Fixes #10071
Closes gh-1294
Resizable: Fix size/position changes in resize event

Fixes #10351
Closes gh-1292
Autocomplete: ESCAPE should not change content of a MultiLine

Fixes #9790
Closes gh-1190