Add simple script to plot the task dump of a rank in an interactive window that offers pan and zoom and readout of the task type

Split the star formation task into two parts: The star formation bit and the resorting bit. Move the sf_count communication to just depend on the first one in order to speed things up.

Added communication functions to propagate the new number of star particles after a SF event has occured.

Fixes and documentation of a few more places where the implementation will need to be updated in the future.

Add some implicit tasks to walk the tree up and down after the multipole initialisation and before the downpass.

Re-introduce the 'end_force' function as a task in order for the cooling function to be called at the right place in the time-step.

Also remove debugging output

Previously worked the other way around, which is incorrect.

When given a range of 0 autorange the tasks and plot the threadpoool using the autoranged limits of the tasks