How to use plugins in Extjs - extjs4.2

Question

I am finding it very difficult to use 'Ext.ux.TabReorderer' as a plugin in tab panel
Ext.define("practical.view.Board",{
extend: 'Ext.tab.Panel',
alias: 'widget.board',
plugins: ['Ext.ux.TabReorderer'],
items:[{
title: 'Tab 1'
},{
title: 'Tab 2'
}]
});
This was throwing an console error saying:
Cannot read property 'init' of null
Upon further investigation found that there is no folder called 'ux' in my extjs. Also a quick search showed me that there is a file named 'Ext.ux.TabReorderer.js' in 'extjs\docs\output' folder.
This is confusing me, how do I add this plugin to my tab panel ?
Edit:
After going through the link provided in the comments by DSF
I added Path in app.js
Ext.Loader.setConfig({
enabled: true,
paths: {
'Ext.ux': './app/ux'
}
});
Also changed the tab panel to include
Ext.require(['Ext.ux.TabReorderer']);
Ext.define("practical.view.Board",{...
...
It is now giving me new errors :
1) Uncaught TypeError: Ext.data.JsonP.Ext_ux_TabReorderer is not a
function (TabReorderer.js)
2) Uncaught Error: The following classes are not declared even if
their files have been loaded: 'Ext.ux.TabReorderer'. Please check the
source code of their corresponding files for possible typos:
'./app/ux/TabReorderer.js (ext-all-dev.js)

Answer 1

I was finally able to fix it.
I moved TabReorderer.js from extjs\docs\output folder to extjs\src\ux.
The reason this didn't work earlier was because I was providing a class name inside the plugins array.
plugins: ['Ext.ux.TabReorderer']
Where it should have been an instance of that class, as shown below
plugins: [Ext.create('Ext.ux.TabReorderer')]
Another way to add plugins would be to use a ptype. For example
plugins: [{ptype: 'cellediting'}]
One can find a list of all the ptypes in Sencha docs
Unfortunately there is no ptype for TabReorderer, so had to stick with Ext.create().
For further reading
http://www.sencha.com/blog/using-plugins-and-mixins-in-your-sencha-apps/