Summary statistics miss deletions where state isn't empty

[jsstevenson]

NC_000003.12:g.10146527_10146528delCT returns

{
    "_id": "ga4gh:VA.hvwBZON5KzQGQazIMpeUu_dmyJ-xN8EV",
    "type": "Allele",
    "location": {
      "_id": null,
      "type": "SequenceLocation",
      "sequence_id": "ga4gh:SQ.Zu7h9AggXxhTaGVsy7h_EZSChSZGcmgX",
      "interval": {
        "type": "SequenceInterval",
        "start": {
          "type": "Number",
          "value": 10146524
        },
        "end": {
          "type": "Number",
          "value": 10146528
        }
      }
    },
    "state": {
      "type": "LiteralSequenceExpression",
      "sequence": "CT"
    }
  }

This means we might want to look at what we have for the other summary methods too since fully-justified normalization may mess with them too.

Originally posted by @korikuzma in #43 (comment)

[korikuzma]

@jsstevenson So this issue has to do with the summary statistics. Before normalization, we see that the variant is a deletion. Typically, VRS represents deletions as state.sequence = "". However, we can see in this case after fully-justified normalization we have state.sequence = "CT". So not sure in summary statistics if we should be giving counts for what variants are before normalization or after.