Now current MOTD series number and position in it are stored in user session
Removed ui/base/stories.lisp because it just duplicates code in ui/pages/story.lisp
Some major changes in stories code

Now authors are able to set theird own short story description.
(Short decription -- text that appears when story is rendered as an item
of stories list.)

And categories are textual now.
Implemented categories displaying for stories in lists
Implemented category displaying and changed voting arrows to Unicode characters