Create defaults for encounter_settings classification and relativeSpeed params

[StephanieKemna]

The values we specify in the encounter_settings.json are fairly static, yet there are no defaults in the STG repo currently.
We could make some of these values defaults, e.g. these:

        "classification": {
            "theta13Criteria": 67.5,
            "theta14Criteria": 5.0,
            "theta15Criteria": 5.0,
            "theta15": [112.5, 247.5],
        },
        "relativeSpeed": {
            "overtakingStandOn": [1.5, 2],
            "overtakingGiveWay": [0.25, 0.75],
            "headOn": [0.5, 1.5],
            "crossingGiveWay": [0.5, 1.5],
            "crossingStandOn": [0.5, 1.5],
        },

so that they are not required to pass in, but optional (if anyone wants to change them).