Small bugfixes

Correct spelling errors in documentation

Kokkos changes

USER-DPD: a variety of small but important bugfixes

Added Kolmogorov-Crespi potential

update AGNI potential for Al, reference runs and output and citation

improve consistency of manual

Fixes for PairAIREBO::bondorderLJ

Uses the sphinxcontrib-spelling extension and requires PyEnchant and
aspell-en to be installed.

Adds the optional make target 'spelling' which produces the file
spelling/output.txt. It contains all words it detects.

Due to the large number of false positives, words in
utils/sphinx-config/false_positives.txt are ignored.

We were sending too much data during pack_comm_hybrid/unpack_comm_hybrid.

this closes #388

this fixes #390