Add more flexibilities

[Nasib555]

add options to

1. get the count/size of the items in the sequence.
2. add Sequence starting/started/ended listeners
3. get the views i.e content, background, dismiss button etc.
4. Animations to highlight the dismiss button
5. Option so that the dismiss button can stay in the bottom of the layout
6. to completely turn off the fade animation (currently, setting duration to 0 make the layout blink