v0.9.1 First deployment on Ethereum mainnet

OpenST v0.9.1 is the first release deployed on Ethereum mainnet combined with the
activation of Simple Token to power the OpenST platform. The OpenST platform
allows Ethereum smart contracts to runs faster and cheaper while leveraging
the security properties of Ethereum's Proof-of-Work. In this release we implement
the first corner stone of the protocol: the ability to stake value on Ethereum
mainnet and mint a new representation of that value on a utility chain,
effectively increasing the computational throughput of Ethereum smart contracts
by allowing parallel execution across chains.

OpenST smart contracts have been restructured to store value separately from
the logic that implements the protocol. v0.9.1 is not yet protocol complete
as the validators are whitelisted and not yet open with stake put forward on
Ethereum mainnet. However, by splitting the protocol implementation into
these two logically separate problems, we can already start working with
member companies and developers to fine-tune the APIs and the developer
experience to build mainstream applications on Ethereum.

  Ethereum mainnet (value)   |  OpenST platform (utility)
  ---------------------------------------------------------------------
      Core - - - - - - - - - - - (Core)
      /                      |      \
     /                       |       \
  Registrar                  |  Registrar
    |                        |        |
  OpenSTValue                |  OpenSTUtility
    \_ SimpleStake           |    \_ UtilityTokenAbstract
                             |         \_ SimpleTokenPrime (base token)
                             |         \_ BrandedToken