[Enhancement] Make environmental damage dealt by mechanics count as caster damage

[Sentropic]

Making it so that damage from environmental sources caused by skill mechanics still counts as damage dealt by the caster. This is so that other plugins can take it into account.

Some examples of how this is useful:

• Vanilla exp drops and item drops
• MythicMobs' threat tables and exp/item drops
• Cancel this damage in case friendly fire is off via other combat plugins
• Any other plugins that care about who killed who

Mechanics affected as far as I can tell are:

• Fire Mechanic
• Explosion Mechanic
• Lightning Mechanic

Proposed by @lordsrubka5 in #477

[lordsrubka5]

For friendly fire, doesnt the plugin already check before applying mechanics if the target is damageable to see if its ally in the targetters?

[Sentropic]

Ohh yeah I forgor