Add createSlideData() to move creation of slide data from convert().

Due to this change, add class variables $params and $body.
And delete $line_count in array:$data.
Insted of that, use count($lines) in this method and count($slideData) in view.
Add SlidePluginTest::testSlideWithParamsForButtons

Test nobutton, noindicator, noslidebutton params.
Fix comment in SlidePluginTest.

* line42: tow => some
Add checkParams() to SlidePlugin.

If input params slide plugin, check params in this function.
Now, adapt nobutton, noindicator, noslidebutton params work!
All tests green!