RPAI 3D Engine

A permission per command, and a reload that reloads

Every /3d command has its own permission now, and /3d reload re-reads the config.

• One permission per subcommand (3dengine.list, 3dengine.scale, 3dengine.reload and so on), plus 3dengine.give.others for giving to somebody else and 3dengine.place.command for /3d place. 3dengine.admin still grants them all, so nothing changes for a server that uses it.
• /3d reload re-reads config.yml. Only pack.host, pack.port and pack.bind still need a restart, and the reload says when one of them has changed.
• /3d quality no longer writes over changes you made to config.yml by hand.
• Using a model item without 3dengine.place now says so instead of doing nothing.
• /3d with no arguments lists only the commands you can use, and tab completion only offers those.
• When SpigotMC has a newer 3D Engine, the console says so, and so does chat for anybody with 3dengine.update (ops by default). update-check: false turns it off.