Dialog: Fix shift-tab handling, focus the correct element

Copy-paste error introduced in df6110c0d424ff3306fdd5576011f2dcf4d242d0

Updates the tabbing test to be more specific about which element should
have focus, instead of only checking if focus is within the dialog.

Ref #9646
Ref #10103
Closes gh-1264
Dialog: Honor preventDefault when managing focus

If event.isDefaultPrevented() is true, the focus management is
completely skipped, assuming the user manages focus manually.

Fixes #10103
Closes gh-1265
Datepicker: Define en and en-US locales based on defaults

Fixes #6682
Closes gh-1269
Build: Reorganize external directory

Put each external library into its own directory.
Move jquery.js to external.

Ref gh-1266
Test: Get all jQuery versions from Bower

Ref gh-1266
Build: Upgrade to grunt-bowercopy 1.1.0

Ref gh-1266
Bower: Change jquery dependency to >=1.6 (don't limit max version)

Fixes #10110
Closes gh-1266
Tests: Use closeEnough() to account for rounding differences

Selectmenu's test suite broke with b0e8380, which changed the padding
used by the menu widget. Selectmenu conditionally adds pixels to the
menu's width, and using closeEnough() accounts for that and the
rounding differences across browsers.

Closes gh-1275
Build: Update DB version for releases
Build: Updating the master version to 1.11.1-pre.
Build: Update license

Closes gh-1257
Slider: Reset positioning when orientation changes

Fixes #10105
Closes gh-1268
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