Changed VELOCIraptor interface to pass output file name at invoke time instead of at initialisation.

Various issues, now reproduces the plots we produced before, also have a new mpiactive column

Only check the matter content against the cosmology if both cosmology and self gravity are activated.

Added GitHub README

See merge request !517

Add a function to check at start-up that the mass content of the simulation matches the given cosmology.

Added ability to select the number of particles in the initial conditions as a runtime parameter for Evrard Collapse

See merge request !518

Use the total no. of particles for the inter-particle spacing calculation instead of the total number of particles local to the node.

More cosmology work

Closes #407 and #404

See merge request !516

# Conflicts:
#   src/scheduler.c