Allow disabling of IME by a jQuery selector

Add the variable $wgULSNoImeSelectors to allow custom
disabling of IME in specific elements.

Add captcha input field id to the exclusion list.

Bug: 41675
Change-Id: Ib03a20c50a4f473e6a58638b85da16659268eb09
Merge "Allow disabling of IME by a jQuery selector"