Resolved merge conflicts and adapted logic to most recent changes in feature branch

Closes #46

The following changes were made:
- the modifications to compute pressure were transferred to a derived class compute pressure/grem
- fix scaleforce was renamed to fix grem
- identifying the grem fix was simplified as fix grem passes an additional argument to compute pressure/grem
- dead code was removed in both files
- checking of arguments was tightened

pair styles born/coul/dsf and born/coul/dsf/cs added

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Initializing pointers in USER-OMP

Initializing pointers in USER-DIFFRACTION and USER-DPD

Initialize pointers in SNAP and SRD

Initialize pointers in RIGID and SHOCK

Initializing pointers in PERI, QEQ and REPLICA

Initialized pointers in MISC and MOLECULE

Initialize pointers in MANYBODY and MC

Initialize pointers in KSPACE

Initialize pointers in GRANULAR

Initialize pointers in CORESHELL

Initialized pointers in BODY

Initialize pointers in ASPHERE

Initialized pointers in src folder