Implement getWizardPage(int pageIndex)

Now, when user wants to go to specific page, he must to list to the page by himself like:
```
selectPage(index);
WizardPage page = getWizardPage();
```
I've implemented simple method `WizardPage getWizardPage(int pageIndex)` to do just that. I believe this will simplify and improve readability of users code.
As part of this PR, I'm  also marking original getWizardPage() as deprecated and replacing it  by getCurrentWizardPage() from the same reason (name getWizardPage is not so clear as getCurrentWizardPage)