[feature] added the feed get all datastream api function implementation
[fix] added missing non blocking version
[fix] comments
[fix] added checking for the case where data send and received correctly
[feature] added example of usage xively in a loop
[refac] used the feed_get_all in asynch examples
[feat] added test of asynchronious feed update
[tidy] cleaned examples and made them usable even if xively not compiled against asynchronious settings