* don't load all Feeds and FeedItems to memory when refreshing the flattr status
    with items received from the flattr api
* added method for resetting flattr status of all feeds and items

This adresses https://github.com/danieloeh/AntennaPod/pull/331#issuecomment-32112929
items 1 and 3.

followup on #331
* include error message from Flattr4j in notification (subText shows message for first failed flattr)
* big extensible flattr notification with full list of error messages

followup on #331
* make FlattrClickWorker drop toast when launched interactively
  as part of a flattr action (by explicitely flattring a thing)
* make it report a notification when it was launched implicitly
  (when refreshing feeds) or when flattring failed

followup on #331