only show animation dropdown if there are multiple animations.
made 'change spritesheet' button extra small.
only show sprites w/ multiple anims in phaser_set_animation block.
Field editors now work on iOS 8.

This is a workaround for google/blockly#17. It's kludgy, but at least
field editors now work on iOS 8, though they might now be broken on
older versions of iOS. I don't have any way of telling, as I don't
have any iOS devices with old versions on them.