do not save sit entities

Now supports spigot!!!

CHANGED

Changed EventPriority to HIGHEST and set ignoreCancelled to true to avoid sitting where you shouldn't be able to.

CHANGED

No more visible pig when you sit a stair.

and some other code, config cleanup.

CHANGED

permissions system:

• now you can configure layouts' permission requirements.
• /sit reload command now requires "sit.command" permission.

y offset now fixed in default config.