- removes redundant code for conflict checks
- updates and expands original check to report fatal error instead of ignoring
  files
- removes obsolete DetectAndRemovePackageHeader and RemovePackageHeader utility
  functions which are no longer needed
- adds utility function DetectBuildSystemConflict, which loops over files and
  reports an error if they exist in the lammps src directory.
- updates definition of LAMMPS_SOURCE_DIR, LAMMPS_LIB_SOURCE_DIR and
  LAMMPS_LIB_BINARY_DIR to be absolute paths. This improves instructions in
  error messages

Expand cmake documentation

Collected small changes and bugfixes for next patch release

Added boxrel example and simplified latte.in

cmake: implicit fortran libs need to linked last

add more thorough checks on parsing reaxff force field and signal when the lgvdw setting is correct.

closes #876

Limit atom energy change in fix dt/reset

Add support for inline format strings to immediate variable substitution

Variable style 'string' substitutes variables in definition

Apply modifications to MEAM & MEAM/C as found by Kyung-Han Kang

Improve fix manifoldforce warning

Add code coverage target to CMake

Bond/react update

Fix the tail correction with pair_nm

Collected bugfixes and updates

cmake: add DOWNLOAD_MSCG option

rebase