rename internal document size to not conflict with public property
rename internal document size to not conflict with public property

chriseidhof/JNWCollectionView,konstantinpavlikhin/JNWCollectionView,Deadpikle/JNWCollectionView,hachidorii/JNWCollectionView,danielmartinprieto/JNWCollectionView,jwilling/JNWCollectionView,regexident/JNWCollectionView,kettch/JNWCollectionView,Spark-Xl/JNWCollectionView