chmod+x
set modelname only when it's being specified

Details:
without this precaution, pyFBU.py crashes on defaultModelFname
delete all the set* methods

Details:
these are not really needed with python
some docstring; cleanup default parameters; vertical compression
prefer assert to sys.exit; clarify removeExistingModelFile; remove vertical space
if we really want to list the authors, do it once
do not need shebang w/out main
move usage from comment to help message

Details:
here it's more useful.
If we decide that the template is a required option, we should make it
a positional argument rather than an option with '-t'