Add <entry[saveName].dropped_entities> for Drop command
Fix a few notable location bugs

Make it work with 'note' command, make it not crash while saving if the
world is removed.
The whole notable system still needs reworking and all that, this is
just a temporary fix for until that can be done.
Make properties slightly less generic, fix security risk

It was possible to do things like "/ex narrate
<p@name[velocity=0,10,0,world]>" to launch yourself in the air, or apply
any other mechanisms to anything else very easily through just a tag...
a tag should never execute code with a visible effect, on the off chance
a poorly written script accidentally exposes free tag-writing to common
players.
This will now only allow tags to apply property/mechanisms if the object
is not in the world (EG, an un-spawned entity, or an item)
NOTE: Inventories are still at-risk, as their data is entirely in props
for some weird reason, and could potentially be used to add items to
an existent inventory or something like that.
Added "player enters notable cuboid" and "player exits notable cuboid"
Full functionality for cuboid enter/exit smart event

- Now fires "exits notable cuboid", "enters notable cuboid", "enters
<name>", and "exits <name>" as separate events. Each event gets its own
contexts and event names in a separate EventHandler call, primary to
prevent issues with the cuboid context being inaccurate/useless if it
contains extra data.
Normally doing it like this might be better to avoid, but
less-than-perfect efficiency should be expected of any smart event...
this won't add any *noticeable* overhead at least.
- ALSO, forgotten notable location patch: clone notable locations when
returning them, so they can't be accidentally modified by commands /
tags that read them.