additional preparation before alterations to main

- various fixes and tweaks to many files in src/, in perparation for
  reworking splatfilch.py.  The following general changes were
  performed:

- .gitignore: cache was missing for some reason, and name of
  config file has changed.

- ArgSetup.py:  simplified argparser-to-dict conversion routie in get_cl_args
- ConfigFile.py:  configparser-to-dict conversion now also handles ints.
- Defaults.py:  changed default last_run date to None.

A note on the last_run change:  I think that given the nature of this
program, last_run is effectively the main requirement. Thus, we
shouldn't be guessing at what it is if we don't know; rather that is an
error, and the user needs to supply it.  It is worth noting too, that
the blank config file generation routine DOES pick the current time when
a file is made, however it is left commented and thus inactive