MDL-55841 core: Allow copy box to be used multiple times in one template

lib/templates/copy_box.mustache

@@ -20,7 +20,7 @@
     Interface element to contain text that the user should copy. Will automaticaly select when clicked.
 
     Classes required for JS:
-    * none
+    * copy_box
 
     Data attributes required for JS:
     * none
@@ -31,10 +31,10 @@
     Example context (json):
     { "text": "Copyable text"}
 }}
-<input type="text" class="copy_box" value="{{{ text }}}" readonly="readonly" id="copy_box-{{uniqid}}"/>
+<input type="text" class="copy_box" value="{{{ text }}}" readonly="readonly" size="48" {{#id}}id={{#quote}}{{{id}}}-{{{uniqid}}}{{/quote}}{{/id}}/>
 {{# js }}
 require(['jquery', 'theme_bootstrapbase/bootstrap'], function($) {
-    $('#copy_box-{{uniqid}}').on('click', function() {
+    $('.copy_box').on('click', function() {
         $(this).select();
     });
 });