Tweak image sizes for Nexus7

I have created a drawable-tvdpi folder for Nexus 7 images which makes the images print out correctly on my Nexus 7 emulator (I had the previous emulator set as the second Nexus 7 release, an xhdpi screen).

I have also bumped up the size of the yak image in the game (I like that picture)

I may need to tweak the yak for Nexus 7 afterwards.