Knockback improve

[SaithTime]

This is a big improvement in knockback, especially useful for practice servers, but it can be useful for Pvp oriented servers.

• First of all, it improves the management of knockback values.
• Improved knockback command with clickable interface (I thought I was going to die).
• Added knockback management for projectiles.
• Added an instant-interaction parameter, this will reduce the delay of the playinuseentity package used in Pvp.

I propose you this PR because you have in your hands the most powerful spigot possible for the creation of a practice server.

[Sculas]

@SaithTime Hopefully there are no conflicts since I migrated the knockback config to static for you to make it the same as the NachoConfig.

[Sculas]

I'll fix the conflict.

[Sculas]

Alright, should be all good now. Will test it now before I merge it :)

[Sculas]

Just tested it and everything works 👍 Thank you for this PR @SaithTime and thanks @Elierrr for helping/reviewing!