Augur compatible output

[rneher]

augur ancestral is a very light wrapper around treetime ancestral and with the new treetime, it would make sense to just replace augur ancestral with treetime ancestral. The main missing requirement would be a "node data json" output.
These json's look like

{
    "annotations": {
        "HA1": {
            "end": 1052,
            "seqid": "config/h3n2/ha/genemap.gff",
            "start": 66,
            "strand": "+",
            "type": "gene"
        },
        "HA2": {
            "end": 1715,
            "seqid": "config/h3n2/ha/genemap.gff",
            "start": 1053,
            "strand": "+",
            "type": "gene"
        },
        "nuc": {
            "end": 1737,
            "start": 1,
            "strand": "+",
            "type": "source"
        }
    },
    "generated_by": {
        "program": "augur",
        "version": "24.1.0"
    },
    "mask": "000011100000000",
    "nodes": {
        "A/AbuDhabi/240/2018-egg": {
            "aa_muts": {
                "HA1": ["T160K", "G186V", "S219Y"],
                "HA2": [],
                "SigPep": []
            },
            "muts": ["C544A", "G622T", "C721A"],
            "sequence": "ACGT..."
        },
        "NODE000001": {}
    }
}

The annotations are really only an instruction to auspice, they could come from somewhere else. Similar for the mask. But the nodes part should be quite easy to generate.