rename Hanning window to Hann window in RealDft
convert integers to doubles explicitly during window computation in RealDft
simplify to_string() for WindowFunction enum class in RealDft
add Bartlett window function to RealDft
add Bartlett window function to InterfaceThread and command-line options
remove unused fPixelToHz lambda from cached settings struct in InterfaceThread
add .clang-format and beautiful target to Makefile
format codebase with clang-format