Read information from traces and configuration

The trace file now separates the fields by "," (comma) instead of
whitespace.

Remove some hardcoded values and read them from trace files and
configuration files.

 - The image is taken from the 7th field in the trace file or the
   'default_image' configuration option.
 - The image size is taken from the 8th field or te 'default_image_size'
   configuration option.
 - The flavor is read from the 9th field or the 'default_flavor'
   configuration option.
Removed unused local variable