Fixes #8335 for 2.0, makes additional simplifications for data module and more

1) Use data_priv methods instead of jQuery._removeData and jQuery._data
2) Update couple comments in data module
3) Simplify Data methods
4) Remove needless, internal second argument of jQuery.cleanData
5) Add Data#accept method
6) Add tests for jQuery.acceptData and #8335
7) Add additional test for jQuery.queue

/cc @rwldrn