move get allocation to gosdk from blobber

[dabasov]

move this function from blobber to gosdk

func requestAllocation(allocID string) (sa *transaction.StorageAllocation, err error) {
	var b []byte
	b, err = transaction.MakeSCRestAPICall(
		transaction.STORAGE_CONTRACT_ADDRESS,
		"/allocation",
		map[string]string{"allocation": allocID},
		chain.GetServerChain())
	if err != nil {
		return
	}
	sa = new(transaction.StorageAllocation)
	err = json.Unmarshal(b, sa)
	return
}