stack for channels when browsing. back button to browse up a level
unsubscribe when browsing out of containers
fixed bug: when going up a level, only unsubscribe if it is not the top level
loadAv half-uses json data
pass id of clicked item to nuvoapiclient, which decides to browse or load the item at that index. get parent item for load request from browse data.
removed all uses of nuvocontaineritem class
removed nuvocontaineritem class