Error checking for configfile and lorax output directory

taskbase:
    * Check that the -c config file exists (and is a file)
    * Implement two new functions that can be used to get
      values from config.ini safely
    * Use ConfigParser everywhere instead of iniparser
    * Check if lorax output directory exists; if does, fail_msg and
      advise rename or delete.
    * Correct minor bug where we avoid a traceback if the profile is
      DEFAULT because has_section does not recognize DEFAULT