added new json api package
added some tests for fromJson method in json_api
added toJson method in json_api and some tests
added tests for toJson BannerInfo
added tests for toJson StatItem
added tests for toJson ReportInfo
update toJson for types GetBannersInfo, GetSummaryStatInfo
update toJson for type NewReportInfo
update toJson for type PhrasePriceInfo
update json_api for User
update json_api for Campaign type
update json_api for PhrasePriceInfo type
have updated all json cases, fixed bugs