Polish the feed reader

[psychcf]

The feed reader needs a lot of work if we want to be able to use it as you would a regular RSS feed reader. The following features must be implemented:

• Feed items should be cached, and updated progressively at a certain interval
• The window title, and each feed item on the tree should have a number in parenthesis indicating how many unread items there are (the window showing the total number of unread items, while the tree items correspond to the individual feed)
• Context menus on the grid, so items can be marked as read and unread
• A throbber on the toolbar to show that a feed is being fetched

[psychcf]

I got new items working for each individual feed, still need to get the global number of unread items working though.

[psychcf]

Just now I got the throbber implemented, and a global number of unread items to show in the window title.

[psychcf]

Good enough. We can always improve it more in 1.1.