Moving_avg model parser is too strict (should coerce numerics)

[polyfractal]

The settings parser for moving_avg models is too strict, and will throw an exception if it encounters a non-double (including coercible numerics). Should be changed to accept any numeric.

E.g.

"movavg": {
  "moving_avg": {
    "buckets_path": "avg",
    "window": 12,
    "model": "holt_winters",
    "settings": {
      "alpha": 0.4992721,
      "beta": 0.1366293,
      "gamma": 1,
      "period": 4
    }
  }
}

{
  "error": {
    "root_cause": [
      {
        "type": "search_parse_exception",
        "reason": "Parameter [gamma] must be a double, type `Integer` provided instead"
      }
    ],
...
}