Conflicts:
	src/hydro/Gadget2/hydro.h
	src/hydro/Gadget2/hydro_iact.h
	src/hydro/Gadget2/hydro_io.h
	src/hydro/Gadget2/hydro_part.h
	src/runner_doiact_vec.c

List top-level cells with tasks

See merge request !441

Fix pair vec exit iteration

See merge request !447

Fix spelling

See merge request !448

Merge branch 'fix_pair_vec_exit_iteration' of gitlab.cosma.dur.ac.uk:swift/swiftsim into fix_pair_vec_exit_iteration

Bug fix: Fix the exit iteration padding.
 - Removes padding for the exit_iteration when looping over cj.
 - Calculates the padding correctly for the exit_iteration when looping over ci

See merge request !446

 - Vectorised version of runner_dopair2_force

 - Expands testActivePair to include more test cases and to also test the force pair tasks 

 - Creates a branching function for DOPAIR2 so that the corner pairs are calculated using the serial version of DOPAIR2

 - pairs_all_force() now checks if particles are active before updating them

 - Added more macros to vector.h to improve code readability.


See merge request !440

Fix various issues with MPI and partitioning

These are two bugs and one feature in the current handling of repartitioning
and MPI tasks.

Extracted from current developments so they do not get lost.

See merge request !436

Fix int-in-bool-context with gcc-7.2

With GCC-7.2.0, I am getting the following error:
<code>
scheduler.c:1606:14: error: ‘<<’ in boolean context, did you mean ‘<’ ? [-Werror=int-in-bool-context]
     if (!((1 << t->type)) || t->skip) continue;
          ~~~~^~~~~~~~~~~~
</code>

See merge request !444

Removed old interaction debugging option and created a new one that is not associated with an SPH scheme.

Large parallel hdf5

Fix to #72. 

This is a workaround to the limitation of parallel-HDF5. The low-level MPI-IO implementations limit writes to 2GB per rank (irrespective of the total amount being written across all nodes). 

The solution involves writing chunks of 2GB (or in practice 2'000'000'000Bytes) and then repeat for the remaining chunks, if any, by shifting the position to write of each node in the file and in memory by 2GB. Ranks that did not pass the threshold just write nothing.
In realistic scenarios we won't need more than a handful of iterations.

See merge request !438