Updated to work with LAMMPS stable_29Oct2020

- Breaks combination with older LAMMPS

Prefixed compile-time options with NNP_

- Also added underscores.
- Changed IMPROVED_SFD_MEMORY (enabled by default) to
FULL_SFD_MEMORY (disabled by default).

Merge pull request CompPhysVienna#73 from singraber/nnp-select_remain…

…ing_set

Tool nnp-select puts out also the rejected cfgs

Merge pull request CompPhysVienna#72 from streeve/cabana_group_init

Cabana: SF group initialization

Fixed bug in makefile

Updated Readme badges

Add more packages in travis script.