How to extend Qt Creator (for example adding plugins) in Qt 5.4?

[HYSuperman]

Now I want to write some of my own plugins in Qt to tailor Qt Creator.

I checked the documentations here, but these documentations seem to only work with the older versions of Qt and Qt Creator. When I copy some of its code samples to my Qt Creator (3.3.2) and try to compile the Qt Creator, some headers are missing.

For example, in this page, it teaches us to write a wizard plugin into Qt Creator. The code samples were demonstrated in the page. There is such a line in a head file webpagewizard.h:

...
#include "utils/filewizarddialog.h"
...

When I paste this line in my Qt Creator, it shows that there's no such header.
I tried to input utils and tab, tab, tab...All I got was this one:

...
#include <utils/filewizardpage.h>
...

So this code cannot be used because there is no fileWizardDialogclass to use.

I went through all the Qt 5.4 documentations, there is no one telling me how to add a plugin into Qt Creator, and there is no documentation about the source of Qt Creator.

Does anyone know how to tailor Qt Creator (3.3.2) in Qt 5.4?
Please tell me, Thanks!