==== Data model: ====
For each subscription, there are some entries in the "feedList" category.
Under this category, there is <subID> with a blank value.
There is also _title_<subID> and _lastRefreshed_<subID> with the corresponding values.
This is used to detect when feeds are removed. We can offer to clear the local cache for these feeds.
This is also used to tell when a feed was last refreshed.


For a given feed, the entries are listed under category "feed_<subID>", with an entry for "<entryID>" with a blank value.
There is also _description_<entryID>, _title_<entryID> and _link_<entryID>.
There is an entry called "latest" that is a comma-separated list of entryIDs
The <entryID> is assumed to be chronological. We'll probably set a limit on the number of entries that can be kept in the cache.


We also persist the tree view of the subscription list. In category "subsTree", the key "subsTree" maps to value JSON(tree).

==== Caching trick: ====
The TiwyFeeds.html file needs to be set to expire correctly to avoir IE warnings during development time