More info about alias origin

[rsuchecki]

Following discussion on slack, additional, optional (?) information could be specified for the evidence underlying an alias, for example type and tool:

    {
        "namespace1": "myGenome:myAnnotation",
        "string1": "my1AGene1",
        "namespace2": "myGenome:myAnnotation",
        "string2": "my1BGene1",
        "evidence": {
            "type": "alignment", 
            "tool": "blat"
            "coverage": 0.9,
            "identity": 0.99
        }
    }

in addition to stating the origin of an alias this would facilitate having alternative sets of aliases selected by the user.