Support complex AND and OR filters

[brettwillis]

Newly added in Strapi 3.1.x
See https://strapi.io/documentation/v3.x/content-api/parameters.html#complexe-queries

[brettwillis]

An or filter, once parsed, comes in the shape:

{
  "where": [
    {
      "field": null,
      "operator": "or",
      "value": [
        [
          {
            "field": "rank",
            "operator": "eq",
            "value": "42"
          }
        ],
        [
          {
            "field": "rank",
            "operator": "eq",
            "value": "82"
          }
        ]
      ]
    }
  ]
}