Topic revamp array validator

Introduce a new ApiPie Array validator for more flexible validations
The following validation are currently supported
* Validates all items of an array has the specified type
* Validates all items are in a set of values

     **exemple 1**
      Assert `hits` must be an array of integer value
      ```ruby
      param :hits, Array, of: Integer
      ```

      **exemple 2**
      Assert each items of `colors` to be in the enumeration 
      ```ruby
      param :colors, Array, enum: [ "red", "green", "blue"] 
      ````

     **exemple 3**
     The load of enum can be deferred until needed. this useful when the enum may changes
     ```ruby
      param :colors, Array, enum: ->  { Color.all.pluck(:name) }
      ````

      **exemple 4**
      Assert `things` is an array of any type
       ```ruby
       param :things, Array
       ````
Is the old usage of Array validator, still compatible with the new implementation ? (ie: no breaking changes)
If not, it should be better to keep the old behavior for the old name for an easily introduction of the new validator.