Reference to a high resolution persistent per-node timer.

Can be obtained using minetest.env:get_node_timer(pos).

set(timeout,elapsed)
^ set a timer's state
^ timeout is in seconds, and supports fractional values (0.1 etc)
^ elapsed is in seconds, and supports fractional values (0.1 etc)
^ will trigger the node's on_timer function after timeout-elapsed seconds

• start(timeout) ^ start a timer ^ equivelent to set(timeout,0)
• stop() ^ stops the timer
• get_timeout() -> current timeout in seconds ^ if timeout is 0, timer is inactive
• get_elapsed() -> current elapsed time in seconds ^ the node's on_timer function will be called after timeout-elapsed seconds
• is_started() -> boolean state of timer ^ returns true if timer is started, otherwise false