Decompose: Add TJsonValueHelper (deprcate TJSONObjectHelper)

[bogdanpolak]

TJsonField = record
  fHasField: boolean;
  fPair: TJSONPair;
  constructor Create(const aField: string; const aValue: Variant);
  function HasDate: boolean;
  function AsString: strong;
  function AsDate: TDateTime;
  function AsInteger: integer;
  function AsBoolean: boolean;
  procedure SetValue(const aText: string); overloaded;
  procedure SetValue(const aDate: TDateTime);
  procedure SetValue(const aValue: integer);
  procedure SetValue(const aValue: boolean);
end;

function CreateJsonObject(aObjectData: TArray<TJsonField>): TJSONObject; 
// function TDataSetHelper.AsJson: TJSONArray;

TJsonValueHelper = class helper for TJSONValue
  function IsJsonArray: boolean;
  function IsJsonObject: boolean;
  function HasField(const aKey: string): boolean;   // expects JSONArray
  function GetField(const aKey: string): TJsonField;   // expects JSONArray
  function TryGetField(const aKey: string; out aJsonField: TJsonField): boolean;
  // --
  procedure AddField(const aKey: string; const aValue: Variant);
  procedure AddObject(aObjectData: TArray<TJsonField>);  // expects JSONArray
  // --
  // LoadFromFile, LoadFromStream, SaveToFile, SaveToStream
  // FromDBField, WriteToDBField - expects not TJSONObject and not TJSONArray 
  // FromDataRow, WriteToDataRow - expects TJSONObject
  // CreateClientDataSet - expects TJSONArray
end;

Sample JSONs (review):

https://stackoverflow.com/questions/24815625/parsing-valid-json-with-tjsonobject-using-embarcadero-code-example-fails-with-ex