* partial implementation of berserk spell (unit does not always attack the nearest creature, wrong handling of situation when nearest stack is too far)
* ballista can shoot (it was considered to be always blocked instead of always free)
* r-click popups on selected town/hero.bonus and teams in pregame
* disabled music due to bugs in SDL_mixer and smpeg (probably it was the source of reported random crashes / hangups)
* minor fixes
* support for 3 new artifacts:
- Ring of Vitality
- Ring of Life
- Vial of Lifeblood
* restructures creature ability preparing (creature abilities are now loaded from cr_abils.txt file). It needs further work - all changes in abilities should be moved from CCreatureHandler.cpp to cr_abils.txt as it's done in this commit (I hope it's clear how it should be done as there is an example)
* fixed slider behavior when showing less maps/games than available slots
* added a few missing sounds for creatures
* fixed problems with artifacts info caused by bug in serialization
* fixed bug in Scholar's serializetion
* all stacks features will be serialized (should fix problems with missing premies from artifacts)
* proper serialization of HeroBonus, fixes some problems/crashes
* resource silos won't give resources on the first day
* fixed problems with removing artifacts when all visiblebackpack slots are full
