Add a PartialCollection class
Add a PartialCollection class

This class will be used when retrieving a range of children in a folder
or a subset of any paged request.

glawson6/box-java-sdk,manywho/box-java-sdk,gcurtis/box-java-sdk,itsmanishagarwal/box-java-sdk,bgoldman/box-java-sdk,box/box-java-sdk,codyebberson/box-java-sdk,TLuthra/box-java-sdk