Widget: Extend .option() to set partial nested options

[joern.zaefferer]

This should work: .button("option", "icons.primary", "ui-whatever")

[scott.gonzalez]

This is complicated by the fact that the widget won't know what's actually changing. Either $.Widget handles the partials and the information of what's actually happening is lost by the time it gets to the actual widget or each individual widget needs to handle the partials. Having each widget handle this would be a bit insane. Perhaps we can have $.Widget handle the partial and covert it to a full hash (mixing in the current values with the new values) and then treating it like the user changed the entire value for the top-level property.

[Scott González]

Widget: Allow setting individual properties of deep options. Fixes #7035 - Widget: Extend .option() to set partial nested options.

Changeset: 6fc98deef03b91b0ea2ed51be2708bdd2c61d479