Performance: replace several jqmData() function calls with getAttribute() to improve performance. It is the same as #5466.

Hi, All.

I saw that #5466 PR was closed by @gabrielschulhof a few days ago. Thanks so much Gabriel. :)
And there are many lines using jqmData() so my team rechecked them what lines could be changed with get/setAttribute. As a result, the committed codes are the same as #5466.

But some other jqmData method calls return true or false value, so my team thought that it would be better to make a new function including get/setAttribute to handle that case.
@gabrielschulhof, you made getAttrFixed() on buttonMarkup.js, so what do you think that we will define getAttrFixed() in global area and use it in other places? If you agree with my idea, we can upgrade more codes to improve performance.

* Tests : The code has been tested on several jQM widgets using qunit.js.
* Modified code is followed the jQuery Core Style guide.
* Scope : Performance improvement.

If there are any problems or mistakes on that PR, please let me know. Thanks in advance.