Refactor ime lazy loading

* Do not load anything unless input field is focused
* Split the setup function to smaller functions
* Introduce $wgULSImeSelectors to allow configuration and avoid
  duplication of selectors in two places.

Change-Id: If5a476e66681dde9f0b72f619d35ddf6255246ac

UniversalLanguageSelector.php

@@ -123,6 +123,19 @@ $wgULSPosition = 'personal';
  */
 $wgULSEventLogging = false;
 
+/**
+ * Array of jQuery selectors of elements on which IME should be enabled.
+ *
+ * @since 2013.11
+ */
+$wgULSImeSelectors = array(
+	'input:not([type])',
+	'input[type=text]',
+	'input[type=search]',
+	'textarea',
+	'[contenteditable]',
+);
+
 /**
  * Array of jQuery selectors of elements on which IME must not be enabled.
  *