see changelog

- spectral index calculation gives the exact same result as in C program
- changed handling of argument checks on command line
  - put into SDSSmodules instead and changed general way it works
    if '' in argument
- finished SDSSnormalization
- added functionality to SDSScompspec in order to run it externally as a
  module
- added further flags to SDSScompspec for coordinate calculations
- added SDSScoordinates. Calls SDSScompspec with different coordinates
  each time and gets a compspec object back.
  - currently broken, because of coord_map.