Minimal replacement of active/crystallized state with single state

[vbuterin]

Depends on #120.

Does not include deeper simplifications that become possible with this approach; this is a fairly simple search and replace.

[prestonvanloon]

Context? Why make this change?

[vbuterin]

It's a protocol simplification (two states down to one) that makes way for other protocol simplifications (adjusting RANDAO instantly instead of at the end of the cycle, among other things), which was not viable before because of re-hashing costs, but is viable now, because of the SSZ tree hashing proposal: #120

[djrtwo]

First pass looks good. A few small notes.

I can handle the merge conflict once we merge in #120