Merge branch 'master' into gravity_fixes

.gitignore

examples/Makefile.am

src/cache.h

src/cell.c

src/cell.h

src/runner.c

src/runner_doiact.h

src/runner_doiact_vec.c

src/scheduler.c

tests/testActivePair.sh.in

tests/testGravityDerivatives.c

tests/tolerance_periodic_BC_perturbed.dat

theory/Multipoles/bibliography.bib

theory/Multipoles/fmm_standalone.tex

theory/Multipoles/fmm_summary.tex

theory/Multipoles/mesh_summary.tex

theory/Multipoles/plot_mesh.py

theory/Multipoles/potential_derivatives.tex