TodoClickCallback should return lineNumber instead of content

[stefan-niedermann]

Multiple lines might contain the same content. Therefore, one can not safely replace the checked/unchecked-checkbox.

The solution would be to provide the lineNumber instead od the lineContent in the callback.

Example:

.setOnTodoClickCallback(new OnTodoClickCallback() {//todo or done click callback
@Override
public CharSequence onTodoClicked(View view, int lineNumber) {
return noteContent.getText();
}```