correct typo in USER-SMD introduced by doc-adjust PR

Multiple documentation adjustments and corrections from Steve and Axel

Fixed sign error on mu for semigrand variant of fix atom/swap

Fix bug in Kokkos EAM

as reported by @evoyiatzis the example is incorrect,
but also a mention of the compute a few lines above.

Fast-forward Langevin functionality included in USER-MISC package

this fixes #1135

Added compute for Polyhedral Template Matching

collecting small changes for potential #839

Small fixes to MEAM/C

Creating Developer.pdf first and Manual.pdf later makes
any warnings from the latter step, e.g. about missing
files in doc/src/lammps.book more visible.