New addition to the test suite: A perturbed version of the 125 cells case



See merge request !341

Updated the scripts running the tests to actually crash if they fail at any iteration and not just on the last one. Code formatting. Do not compile the FFT functions if FFTW is not found.

Split the drift into hydro and gravity drift tasks. Implement FFT task and dependencies

Changes:
 - Two drift tasks, one pert particle type.
 - FFT task with gravity ghost tasks for the dependencies.

It passes my usual tests but could you make sure it does not break anything ? That should be the last big change. The rest of gravity should be contained within the tasks themselves.

See merge request !340

No limit on h in test125cells. Add more digits to the output. Perturbed version of the test125cells now works.

Conflicts:
	tests/test125cells.c

These fix a bug in the range of adjacent tasks of the same type
(and colour) which meant they merged into a single bar, regardless
of whether there was a gap or not (feature of span_where).

Also update to offer proper command-line options, the main one of
which is --expand. That splits the tasks of a thread into "expand"
lines of tasks, designed so that adjacent tasks will not be on the same
line. It is now also possible to set the size of the output graphic.

The colours have also been tweaked once more.

Reset the task debugging timers every time-step

Fixes #306.

See merge request !339

Update test kernel

Removes `doself1_density_vec_2` function. Updates `testKernel.c` to include tests for `kernel_deval_1_vec` and `kernel_deval_2_vec`.

See merge request !338