Array<Entity> became as Array<::Dynamic>

`var entities:Array = new Array();`
where Entity is a regular Haxe class. This code is translated to:
`::Array< ::Dynamic> entities = ::Array_obj< ::Dynamic>::__new();`

And to get access to any element of that array Haxe generated this code:
`::lib::entities::Entity e = entities->__get(i1).StaticCast< ::lib::entities::Entity >();`

Would be nice to avoid this StaticCast and generate arrays as `Array< ::Entity>`;

I measured execution time for element access and here is what time I got.
```
StaticCast (generated by Haxe): 3.10301402350888e-07
_hx_array_unsafe_get (using cpp.NativeArray): 0.0353070371420472
Removed StaticCast by hands: 0.0411155711772153
```

Start by tracing the hxcpp code generation for `Array` and compare it with the generated `Array` and `StaticCast` shown in the issue. Use the reported element-access measurements as a baseline; done means generated arrays preserve the entity type without the unnecessary cast and the behavior is covered by an existing or newly located test.

Written by the indexing model from the issue text.