MikroORM smart conditions support

[l00k]

I have added support to MikroORM smart query conditions in forked repo. So now such requests are possible:

{
  variables: {
    "filters": {
      "and": [
        { "id": { "lt": 3 } },
        { 
          "name": { 
            "like": "test", 
            "nin": [ "tester" ]
          } 
        }
      ]
    }
  }
}

One sad thing "$" character is not supported in GraphQL so I had to use plain "eq", "and", "in" not "$eq", "$and", "$in". This may limit somehow use but still I think it is convenient.

If you would like to somehow merge it - you are free to go ;)