Select widget relative item fixes

Changes:

ve.ui.SelectWidget.js
* Make getRelativeSelectableItem properly loop around
* Replace confusing and broken getClosestSelectableItem with getFirstSelectableItem since that's the only use case we had for it anyway

ve.ui.PagedDialog.js, ve.ui.LookupInputWidget.js
* Update calls to getClosestSelectableItem to use new method

Change-Id: I2399d01a45c43d1ad663ed6c6de156e796065306
Merge "Select widget relative item fixes"