Add basic LJ potential*

- Add PairPotential Abstract class
- Add Lennard-Jones potential that should work with both CUDA and C++
  code
- Add tests on HOST side for LJ potential

src/CMakeLists.txt

@@ -4,14 +4,13 @@ set(HEADER_FILES
     particle.hpp
     simulation.hpp
     box.hpp
-    pair_potentials.hpp
+
 )
 set(SOURCE_FILES
-    pair_potentials.cpp
 )
 
 # The library contains header and source files.
-add_library(${NAME}_lib 
+add_library(${NAME}_lib INTERFACE
     ${HEADER_FILES} 
     ${SOURCE_FILES}
 )