Rewrite ScrollDirectionListener to work with list's which inequally high listeitems
Merge branch 'sreichholf-master'
Refactor code. Simplify ScrollDirectionRecyclerViewDetector
Delete deprecated getListViewScrollY()
Delete an extra line
Add the isVisible() getter
Refactor code

* Rename ScrollDirectionDetector -> AbsListViewScrollDirectionDetector
* Rename ScrollDirectionRecyclerViewDetector -> RecyclerViewScrollDirectionDetector
* Make AbsListViewScrollDirectionDetector, RecyclerViewScrollDirectionDetector and ScrollDirectionListener package private
* Convert class members in FloatingActionButton class to local variables(mOnScrollListener, mRecyclerViewOnScrollListener, mListView and mRecyclerView)
* Set scroll threshold with a setter
Add support for the ScrollView
Replace 'for' loop with 'foreach'
Delete outdated Javadoc
Refactor code. ATTENTION! Breaking changes

* Significantly specify custom listeners
* Rename detector classes
* Change type of a custom listener to the ScrollDirectionListener
* Make dectector implemnentation classes private
Make ScrollDirectionListener public
Delete outdated Javadoc
Add Vocabletrainer to the apps list