Add seriallizing support for nsarray objects and Added deseriallizing from jsondata to NSArray

Add seriallizing support for nsarray objects 

for example

Model *m1 = [[Model alloc] init];
// ... set properties for m1
Model *m2 = [[Model alloc] init];
// ... set properties for m2

NSArray * models = [NSArray arrayWithObjects:m1,m2, nil];

NSData* jsonData = [models JSONData];
NSLog([models JSONString]);

=======================
Added deseriallizing from jsondata to NSArray

for example

 NSString* path =  [[NSBundle mainBundle] pathForResource:@"model" ofType:@"json"];
    
    NSData *jsonData =[NSData dataWithContentsOfFile:path];
    id rtn= [NSObject objectOfClass:@"Model" fromJSONData:jsonData];
    if([rtn isKindOfClass:[NSArray class]]){
        // json is a collection of models
    }else if([rtn isKindOfClass:[Model class]]){
        // json is a single model
    }