Fix InventoryView JD formatting (temp separate commit for visibility)
Add Beacon API. Adds BUKKIT-2842

Squashed messages:
Specify that return is a BeaconInventory.

Add BeaconPaidEvent. Partially adds BUKKIT-2842

Change beacon API - remove activation override, add canSeeSky()

Add setNewEffects() to BeaconPaidEvent

Add beacon Properties to InventoryView.

Add radius & activation override, getDefaultEffects

API Changes: narrow getEffects, use ActivationState enum

Remove setDefaultEffects, add note to header about beacon gui

Specify stricter getHolder() in BeaconInventory

Initialize cancelled in BeaconPulseEvent

Cleanup - javadocs & imports