protection check + remove only entities spawned by this mod

[a-tour-ist]

What the title says.

Why/how does the protection check work:

on_dig defaults to core.node_dig.

core.node_dig does a búnch of very important stuff:

• protection check
• logging
• add wear to tools
• run further callbacks from the node def
• run the callbacks from core.registered_on_dignodes (p.ex rewarding xp, ...)

if you provide a custom on_dig function, you have to make sure your node implements these features correctly too.

But there is no need to provide a custom on_dig here, after_dig_node can do the job as well. (In fact it is called by core.node_dig once that function has made sure that the node can be removed)