MDL-56719 mod_chat: clarify 'course theme' change

Plus remove some pointless code.

mod/chat/gui_ajax/index.php

@@ -73,7 +73,6 @@ $modulecfg = array(
     'home' => $CFG->httpswwwroot.'/mod/chat/view.php?id='.$cm->id,
     'chaturl' => $CFG->httpswwwroot.'/mod/chat/gui_ajax/index.php?id='.$id,
     'theme' => $theme,
-    'showcoursetheme' => 1,
     'userid' => $USER->id,
     'sid' => $chatsid,
     'timer' => 3000,

mod/chat/gui_ajax/module.js

@@ -118,11 +118,9 @@ M.mod_chat_ajax.init = function(Y, cfg) {
             this.thememenu = new Y.YUI2.widget.Menu('basicmenu', {xy:[0,0]});
             this.thememenu.addItems([
                 {text: M.util.get_string('bubble', 'mod_chat'), url: this.cfg.chaturl + '&theme=bubble'},
-                {text: M.util.get_string('compact', 'mod_chat'), url: this.cfg.chaturl + '&theme=compact'}
+                {text: M.util.get_string('compact', 'mod_chat'), url: this.cfg.chaturl + '&theme=compact'},
+                {text: M.util.get_string('coursetheme', 'mod_chat'), url: this.cfg.chaturl + '&theme=course_theme'}
             ]);
-            if (this.cfg.showcoursetheme == 1) {
-                this.thememenu.addItem({text: M.util.get_string('coursetheme', 'mod_chat'), url: this.cfg.chaturl + '&theme=course_theme'});
-            }
             this.thememenu.render(document.body);
             Y.one('#choosetheme').on('click', function(e) {
                 this.moveTo((e.pageX - 20), (e.pageY - 20));

theme/upgrade.txt

@@ -3,7 +3,8 @@ information provided here is intended especially for theme designer.
 
 === 3.2 ===
 
-* All themes have "course theme" option for mod_chat (it was just bootstrap2 based themes).
+* mod_chat will not display the 'course theme' option for all themes (previously it was only displayed on
+  bootstrap2 based themes).
 * A new theme config 'undeletableblocktypes' allows a theme to define which blocks are deletable.
 * A new core setting now enables admins to upload the logos of their site. Using the
   following methods, themers can instantly support branding logos without the need