If players are invisible, NodeCore will not add any visible or
audible effects for them, allowing such players to be completely
non-interactive with gameplay.
This allows things like spectator or stealth-admin mods to
function properly.
Standardize the "play a sound for everybody except the player who
is already playing it client-locally" logic into one place.
Fix failure to correctly detect tool speeds for some things, i.e.
when the player is using a tool but the capability used on a node
is actually inherited from the hand.
Note that this may allow pummeling with wrong tools (e.g. repacking
soils with spades) along with accompanying inappropriate tool wear,
but this should be minor and avoidable, and can be fixed later...
