Add semantic exit functions and review exit statuses.

config.cfgrep does better job at hinting how the function works
(i.e. somehow similar to UNIX grep) and that the use is not limited to
INI files.

Also default config file suffix is now "conf".

 *  Add colors,
 *  print ffoo version,
 *  honor TF_DEBUG and TF_VERBOSE from environment,
 *  use nicer but smaller ASCII-art
 *  and include test name in subtest name.

"read strategy" is too ambiguous.  What is really happening is that we
are "merging" the (posible) files into one stream.

Now by default iniread will stop at first file; old behavior can be
restored by -j|--join switch.

Since it's normal e.g. for a dependency to import the same module as
upstream, the warning only created unnecessary noise.