Feature/add feature selected picture

[SuperBeagleDog]

A lot of users asked a feature that the MatisseActivity page can select those pictures users selected before by default.

So that I add a new api for it:
SelectionCreator.setSelectedItems(ArrayList<String> list)
This worked well.

Use case:

   // Define a list to cache those pictures selected by user
   private ArrayList<String> selectedList = new ArrayList<>();

   // Save selected pictures.
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == REQUEST_CODE_CHOOSE && resultCode == RESULT_OK) {
            selectedList.clear();
            selectedList.addAll(Matisse.obtainPathResult(data));-
        }
    }

   // Open the album
   Matisse.from(SampleActivity.this)
                        .choose(MimeType.ofImage(), false)
                        .countable(true)
                        .setSelectedItems(selectedList) // pass those selected pictures.
                        .forResult(REQUEST_CODE_CHOOSE);