Fix actions started from the message list context menu

This patch makes sure actions started via the context menu operate on
the correct message even when the message list changes and the 'adapter
position' accessible via the menu object points to another message.
When the message the menu was opened for is deleted the context menu
will be closed.
Remove changelog entries from the 4.4 branch
Update changelog
Bumped manifest to 4.503
Updated Japanese translation of the changelog.
Refactor code to create LocalFolder instances from a database query.
Don't load unread/flagged count when creating LocalFolder instances

This avoids a potentially expensive LEFT JOIN when querying the database.
Bumped manifest to 4.504
verify res/raw/changelog.xml for an entry for the version being bumped to before changing anything for target bump-version.