Revert "Changed deprecated function gettimeofday which has a resolution of microseconds to clock_gettime which has a resolution of nanoseconds. All functions in now.cpp/hpp are now in units of nanoseconds."

This reverts commit 2cf038f01cb5dbf019fdd17c15d11988907e5d9f.
Revert "change base_experiment.hpp and static_fft to use nanoseconds"

This reverts commit 45804eb572f28f774292fea861308367c117dda4.