renamed files for consistency

src/modules/butterflies/CMakeLists.txt

src/modules/butterflies/butterflies_actions.c

src/modules/butterflies/butterflies_actions.h

src/modules/butterflies/butterflies_generations.c

src/modules/butterflies/butterflies_generations.h

src/modules/butterflies/butterflies_main.c

src/modules/butterflies/butterflies_vital_rates.c

src/modules/butterflies/butterflies_vital_rates.h