Reduce INITIAL_WINDOW_HEIGHTS_LOAD.

Two screens ahead is unnecessarily big and could cause noticeably
slower refresh, particularly in headlines view.
Finalize all statements and close the connection on shutdown.

Fixes issue #40.
Fix completely broken favicons refreshing.
Entire Brief's tab should be reloaded when changing the custom style.

Custom style can be also applied to Brief's XUL document, after all.
FeedUpdateService should just hand the parsed feed as it is.

FeedFetcher.handleResult() does some preparations before handing
the data to FeedProcessor. The intention was for it to map the
necessary data to Brief's container, so that FeedProcessor didn't
have to deal with native feed interfaces. However, we now use
various properties that aren't represented in the containers and
we end up accessing wrappedFeed to bypass them anyway.
Pass the feed's DOM document to FeedProcessor.
Store and use the feed's language.

Feed's language can be specified via RSS <language> element or xml:lang
attribute set on the root element in Atom feeds. It is then used to set
lang attribute on the article container in the feed view.
Detect right-to-left languages and set text direction accordingly.

Solves issue #34.
Specify language of feed view document based on selected locale.

This sets the overall language of the document and applies to such
elements as day headers in headlines view and the empty view
messages. Feed articles have their language set separately,
as declared by feeds themselves.

This is necessary to correctly handle upper-case text transform
in Greek (issue #41) and possibly other language quirks too.