Update OOjs UI to v0.1.0-pre (51f922ba17)

New changes:
1ba6137 Make fieldsets and stack panels more compact
584ed14 Convert styles to LESS and implement grunt task
ad906c5 Add documentation for -1 tabIndex option, which disables tab indexing
3f962db Manage active state of BookletLayout pages
5f3ee83 Disable vertical scrolling in continuous layout mode
96ae071 Make text inputs gray when disabled
51f922b Refactor OutlineControlsWidget, add remove button

Note that 51f922b requires the addition of another message to resources/Resources.php
(eww): ooui-outline-control-remove.

Change-Id: If55f8a78f410f35e38f40a9884d7057c50a4610f
Merge "Update OOjs UI to v0.1.0-pre (51f922ba17)"