New skill system, with new classes SkillInfo.java and SkillManager.java
Changes to SkillUser forces changes in downstream Race and LPlayer classes.
Using some this references in various classes.
Allow changing Mana costs and description in Skill.java
Fix imports in some classes.
Merge branch 'skills' into yaml-loading

Conflicts:
	src/main/java/net/dawnfirerealms/legends/core/LPlayer.java
	src/main/java/net/dawnfirerealms/legends/library/database/YAMLDataSource.java