* added unit test for exporting models with global key mapper * added unit test for exporting models with own key mapper to string
* added unit test for exporting models with global key mapper
* added unit test for exporting models with own key mapper to string

dalu93/JSONModel,jianwoo/JSONModel,dbachrach/JSONModel,db42/JSONModel,CareEvolution/JSONModel,LiuShulong/JSONModel,scottdinggo/JSONModel,huiping192/JSONModel,liuyujing/JSONModel,iwakevin/JSONModel,youprofit/JSONModel,hfossli/JSONModel,johnmyqin/JSONModel,redlinesolutions/JSONModel,yunzhongyoulong/JSONModel,MellongLau/JSONModel,cczallen/JSONModel,MaWenxing/JSONModel,icanzilb/JSONModel,SanjoDeundiak/JSONModel,billinghamj/JSONModel,zwcshy/JSONModel,jsonmodel/jsonmodel,xunan623/JSONModel,SummerHF/JSONModel,kerrmarin/jsonmodel,ThirakornP/JSONModel,billinghamj/JSONModel,zhou18520786640/JSONModel,SatanWoo/JSONModel,jianwoo/JSONModel,liwangbest/JSONModel,SongYuJie1989/JSONModel,SampleLiao/JSONModel,chenkaige/JSONModel,izrie/JSONModel,TerryAsh/JSONModel,xxclouddd/JSONModel,yarec/JSONModel,ramoslin02/JSONModel,zwcshy/JSONModel,ernestopino/JSONModel,AlJaMa/JSONModel,NiuMengFei/JSONModel