support for saving config options into hdf5

configuration is saved into the Space-HDF5 file using Space.tofile()
all config options from the config file and those added on the command line
are saved, however, comments from the config file are ignored.

from the command line the configuration information can be optained using:

binoculars.py info --config file.hdf5

additionally an --extractconfig option is available for the info command:

binoculars.py info --extractconfig out.conf input.hdf5
fix a small bug: rename 'file' to 'filename'

file is a builtin word in python and it was also used wrong once in the call
of the Exception