Improved readoptions.py
This change improves the handling of SoFiA parameter files in readoptions.py. To begin with, I added a list specifying the data types of all parameters such that the correct conversion is carried out irrespective of the actual parameter value. E.g., a '1234' in the input file name field will now be correctly converted into a string rather than an integer value.
Secondly, I cleaned up the code a little bit by adding/updating comments, diverting error messages to stderr rather than stdout, and improving little bits and pieces throughout the code.