Update pocket.yaml, and terrain-pocket.png

Changed all blocks to match PC names, and improved data, texture. (As of v.1.2.0.0)
IMPORTANT! New terrain-pocket.png: http://i.imgur.com/QoblpD6.png

- I don't have much time as before so I can't keep updating to match PC like I used to. I will be very thank you if you guys can also edit pocket.yaml when you work on new names. I have to go through every single blocks but PC team knows where changed. Nearly all blocks are updated. I will occasionally edit some texture and pocket's unique item ids, so please help me work more easily on MCPE part alone. I know block definitions is not all of what you do... I will totally manage and do cleanups on both files when I have time...