Make the list a bit easier to handle in scripts (colon does not have
special regex meaning).

Also im human-readable contexts, dot makes it more likely to confuse the
string with with filename (eg. `foo.bar`.)  But then again, it's better
for humans to go a bit further and decorate the reference, eg.
`foo:bar()` or `foo:$BAZ`.  (Doing that in default output would make
them hard to parse, though.)

Allow for re-use and more independent testing.

Also a first POSIX-oriented library!

These were never intended to be used outside _pretty_color; the fact
that _pretty_color is internal does not mean *its* internal globals do
not need to follow underscore rules.

These variables are not specific to shellfu internals but in all ways
specific to pretty.sh module.  The prefix is mostly historical cruft.

Let's clean that up.

Old naming is inconsistent from how functions are named, which can be
pretty confusing.

Also, there's no such naming requirement for user's modules; the
recommended way is to use unique project-specific prefix for both
functions and globals.

Risk of conflict should be managed by naming modules uniquely and/or
being careful with deployment in new environments.

Main changes:

 *  Removed ability to guess, search and merge files.

    Old inigrep was doing too much.  Instead of just being "grep for
    INIs", it tried to guess file arguments, look for data in local
    folders and smartly merge files based on locality, effectively
    becoming sort of a configuration registry tool.  While that function
    can be (and was) highly useful, it is vastly outside inigrep's main
    purpose; coupling like this made inigrep much harder to understand.

    At the same time, only saturnin applications really used this;
    so it became obvious where such behavior belongs, so relevant
    code was moved to saturnin__conf, which now acts as wrapper around
    the new inigrep.

 *  Rewrote API.

    Old API was designed around the original idea, long long time ago,
    when use cases were not clear yet. This fact propagates as the old
    API being a bit gimmicky, too "granular" with little usability gain
    but great graspability loss.

    New API, on the other hand, simplifies section/key syntax and
    concentrates on few simple modes, easy to understand and/or ignore.

 *  Added module-level documentation.

    Now that shellfu-doc can work as manpage reader, it would be shame
    to not include at least some basic documentation inside modules.
    inigrep (albeit being one-function module) is proud to be the first
    one in shellfu core module set to have at least simple introduction.

Great rewrite with revamped CLI, many added features and bugfixes.

 *  New CLI optimized for simple use.  Default action is to show
    module doc in manpage viewer.

 *  Respects variable documentation.

 *  Respects module documentation (first stray docstring).

 *  Can export (ugly but usable) module docs as Markdown, POD or
    manpage.

 *  Dropped useless features as --cat (one can always open the file)
    or display of partial documentation.

 *  Provided more rich usage hint.

 *  Rewrote tests with focus on more probable scenarios.