Bump version

Overview of changes:

 *  Properly filter subcommands on listing

    In contexts like main --help and tab completion, Saturnin would show
    also arbitrary files from libexec that did not start with dedicated
    prefix ($SATURNIN_LIBEXEC_PREFIX).  This was a mistake and was never
    intended to work that way.

 *  Hook code is now run as separate bash process

    Running it within sub-command code was a little bit too unsafe;
    there's no need to be evil^Weval here.

 *  Rewrote saturnin__version() (used for app --version)

    Newly, --version will only incorporate tagline if it was defined in
    mkit.ini.

    Also "Powered by Saturnin" line has been added so that we don't have
    to ask user every time.

 *  Added --saturnin-get-saturnin-version

    It's a good idea to include this with test reports and the like so
    we're making it more accessible to scripts.

 *  API documentation clarifications

 *  Codebase maintenance

 *  Refactoring for code readability

mkit.ini

@@ -1,7 +1,7 @@
 #mkit version=0.0.14
 
 [project]
-    version     = 0.4.2
+    version     = 0.4.3
     codename    = DoktorV
     name        = Saturnin
     tagline     = Spirit of your toolbox