use named threadfactory for AbstractDeallocator
moved dynamicMapperLookup from ObjectMapper to 
new class
create maker interface for dynamic array handling
add separate method to write the body of objectmapper mapping

this is necessary for our ArrayMapper which explicitly encodes array fields of type array,
as it creates mapping like this:

array_field: {
  type: array,
  inner: {
    type: object,
    dynamic: true,
    properties: {
      ...
    }
  }

and for this only the body without field_name: { ... } is needed.
add possibility to inject a DynamicArrayFieldMapper