Change where the division is when calculating average so that it is not repeated. Use variables for threads.
Put the write data to mrc file in the em2np file instead of tomo.py. Add function to convert npy file to mrc. Reflect these changes in other files (tests).
Add possibility to average.py to process only files where their filename number falls within a certain range.
Allow to choose start and end range with command line
Merged branches, some minor merging conflicts (eg with use_threads)