Inserts a (unread/total)" items count in front of each subcription
on the feeds page.
models/feed.php adds two functions: get_feed_unread_counts(), get_all_w_counts().
get_feed_unread_counts - returns either an array of (unread/total) counts indexed
by feed id or a singl (unread/total) for a specific id.
get_all_w_counts() returns the same as get_all() but appends items_unread and
items_total columns.
controller/feed.php modifies Router\post_action('refresh-feed',function() to
retrun the (unread/total) count in the retruned ajax json array.
Router\get_action('feeds',function() was modified to call get_all_w_counts().
templates/feeds.php was modified to insert the (unread/total) count into the
span id="loading-feed-" such that is can be updated after a refresh.
assets/js/feed.js was modified to to have the Update and hideRefreshIcon
update the returned (unread/total) amounts in the "loading-feed" span.
Essentially, if an enclosure tag exists in the item, then the item menu will contain
a link 'multimedia [speaker symbol]' to the media url. Otherwise, if there is no
enclosure tag, there is no menu item shown.
This feature required adding an enclosure column to the items table (models/schema.php)
and bumping the DB version to 21 (models/config.php). I also added enclosure tag logic
to the Rss20 parser, the model/item.php and template/item.php files.
