Read available inputs from input list, not device structure

[tim-tx]

E.g. for the gate below, use in1 first, then in2.

{
    "collection": "structures",
    "name": "S4_SrpR_structure",
    "inputs": [
        {
            "name": "in1",
            "part_type": "promoter"
        },
        {
            "name": "in2",
            "part_type": "promoter"
        }
    ],
    "outputs": [
        "pSrpR"
    ],
    "devices": [
        {
            "name": "S4_SrpR",
            "components": [
                "#in2",
                "#in1",
                "S4_SrpR_cassette"
            ]
        },
        {
            "name": "S4_SrpR_cassette",
            "components": [
                "RiboJ10",
                "S4",
                "SrpR",
                "ECK120029600"
            ]
        }
    ]
}