Remove required logIndex and transactionIndex for light client support

[jleeh]

Example transaction receipt from light clients for a fulfillment tx:

{
    "jsonrpc": "2.0",
    "result": {
        "blockHash": "0x6c0deace15b5fed0fc3c66d2e1089bbe523960a01a258c5c97bb31c0baad15e7",
        "blockNumber": "0x56c820",
        "contractAddress": null,
        "cumulativeGasUsed": "0x10a30",
        "from": null,
        "gasUsed": null,
        "logs": [
            {
                "address": "0xec8ea88b10717ad268e30bbbf3f3659c44d49256",
                "blockHash": null,
                "blockNumber": null,
                "data": "0x",
                "logIndex": null,
                "removed": false,
                "topics": [
                    "0x7cc135e0cebb02c3480ae5d74d377283180a2601f8f644edf7987b009316c63a",
                    "0x177deec7b77150208732595dafba8fb087c07f87bf2ee095a8566cdf87831afe"
                ],
                "transactionHash": null,
                "transactionIndex": null,
                "transactionLogIndex": null,
                "type": "pending"
            },
            {
                "address": "0xec8ea88b10717ad268e30bbbf3f3659c44d49256",
                "blockHash": null,
                "blockNumber": null,
                "data": "0x",
                "logIndex": null,
                "removed": false,
                "topics": [
                    "0x794eb9e29f6750ede99e05248d997a9ab9fa23c4a7eaff8afa729080eb7c6428",
                    "0x177deec7b77150208732595dafba8fb087c07f87bf2ee095a8566cdf87831afe",
                    "0x0000000000000000000000000000000000000000000000000000000000006941"
                ],
                "transactionHash": null,
                "transactionIndex": null,
                "transactionLogIndex": null,
                "type": "pending"
            }
        ],
        "logsBloom": "0x00000000000000000000020000000000000000000000000000000000000000000000100000000000000000000000000000800000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000000000000000000100000000000000000000000800000000000000000000100000000000000040000000000000000000000000000000000000000000000000000004000000000000000000102008000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000000",
        "root": null,
        "status": "0x1",
        "to": null,
        "transactionHash": "0x2f6dafc0e47bfbf98a9d402e901e7b1d13ba04abe0411a5073b6f7aef379873d",
        "transactionIndex": "0x1"
    },
    "id": 1
}

On finding usages for transactionIndex and logIndex in models.Eth, the only use was it being printed in the logger in debug mode:
https://github.com/smartcontractkit/chainlink/blob/master/core/services/subscription.go#L109

[jleeh]

Closing this as it's a Parity bug rather than a deviation in response from light clients:
openethereum/parity-ethereum#10697

[jleeh]

Re-opened this to workaround the issue before the parity bug is fixed.