instance zone is finished.

Reported by: ShinichiYao  

- Replaced SkillData.getInstance().getSkill with SkillHolder DTO;
- Replaced Skill versions of doCast and doSimultaneousCast with
SkillHolder ones;
- Fixed typo on Sanctum of the Lords of Dawn instance zone;
- Some cleanup.

 - Reported by: ShinichiYao

- Based on St3eT's work

Fixed minor typos.

Moving all files to main folder.
Using Gradle to define, manage dependecies and build the project.
Upgraded Gradle wrapper.