Animation of NIPoSTs chaining

[lrettig]

Add it here: https://github.com/spacemeshos/protocol/pull/5/files/5a09f8a52a687194ce127a29c9ed635dc1945d68#diff-3ce2aee4b1e938c9c876b8e205b9f867R38

CREATE VERTICAL ANIMATION TO ILLUSTRATE THE NIPOSTS CHAINING: initialization -> poet -> execution -> poet -> execution -> poet -> ….