* Replace reqClass by reqSkillVlaue field in `skill_discovery_template`
and check expected skill points amount for specific reipe discovery.
* Add new `spell_loot_template` loot table for store item selection data for spells.
At this moment for expclicit recipes discovery spells.
* Code cleanups.
* Implement SPELL_EFFECT_CREATE_ITEM_2 (157). This alos let work many item creating spells.
* Add `skill_discovery_template`.`reqClass` for allow clas specific racipes storing in table.
* Make primary key for `skill_discovery_template` pair (spellId,reqSpell) that allow have duplicate recipes for different reqSpells.
* Implement SPELL_EFFECT_SCRIPT (77) cases for explicit recipe discovery spells with learn spell selected by `skill_discovery_template` data.
Note: as expected explicit recipe discovery abilities always return some spell while exist any not learned yet for player class.
