Create cleaner versions of onBeforeDropBag and onBeforeUseItem

Foreword

All new events in IWD should adhere to the following two rules:

1. Event should not be prefixed by on...
2. Event should only accept a single argument (an event object which contains whatever is needed)

onBeforeDropBag -> beforeDropBag

Old arguments:

(obj: 'object that does the dropping', items: 'array of items to be dropped', killSource: 'object that caused the drop to happen')

New arguments:

{
    objDropper: 'object that does the dropping',
    objLooter: 'object that will be looting',
    objKillSource: 'object that caused the drop to happen',
    items: 'array of items to be dropped'
}

onBeforeUseItem -> beforeUseItem

Old arguments:

(obj: 'object that is using the item', item: 'item that is being used', eventMessage: { success: 'boolean', cdMax: 'integer' })

New arguments:

{
    obj: 'object that is using the item',
    item: 'item that is being used',
    cdMax: 'integer that can be overridden if needed',
    success: 'boolean'
}