reworked hardMode and oreXp drops

[TheGoldenKnight]

Added:

• restrictOreExperienceDrops tags used to restrict what blocks drop Levelz's experience orbs
• Config option for restrictOreExperienceDrops
• Adjustable respawn options. Refunding levels, skill points and skill levels.
• Config option for levelRetainPercentage (how much of levels in %, rounded down, to keep after respawn) and levelRefundSkillPoints (if player should keep skill points in assigned skills or be fully refunded)

Fixed:

Changed:

• hardMode config usage deprecated

Notes:

The code seems stable, may need to do a cleanup later but otherwise it works as intended.