Context

Added INCREASE_COUNTER and GET_COUNTER instructions in Michelson.

INCREASE_COUNTER adds an operation on the top of the stack, corresponding with the increase operation of the global counter
GET_COUNTER adds on top of the stack the int value of the global counter. Note that in this approach, GET_COUNTER won't takle into account the INCREASE_COUNTER operations since the operation's are not executed until the contract is finished executing.

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