Removing duplicate functions to avoid some merge issues for other branches

Master is broken, so back to original for now.

This reverts commit 409531ab.

For cells with large counts this matters

Conflicts:
	src/task.c

Need to do this as a pre-init stage to task marking which will unskip tasks that have active cells

Hydrodynamics in 2D + New test cases

This adds the ability to run SWIFT in 1D and 2D. There is a large number of hydrodynamics tests that only exist in 2D so we will now be able to run them. This implements #145.

I have also renamed a few of the test-cases to specify the dimensionality of the problem. 

The Gresho-Chan vortex test-case can now be run and give the expected answer (provided the code is compiled with 2d hydro in const.h). The run.sh script runs the code, plots the solution and makes a movie out of everything.

See merge request !216

Also make the recursive call to a local fully typed function

Removed explicit references to p->rho_dh in the test27 and testPair unit tests as these might not exist in all hydro schemes.

Now at least as fast as tkask version