Drop confusing splash cmdline and --enable-progress configure option

This patch reverts back to the progress/status behavior of Finit < v3.0
because this is what most users expect, including the maintainer.  The
resulting code and configure script is a lot simpler to understand and
maintain:

- No more --enable-progress or --enable-progress-classic configure
  flags.  Instead a progress_style variable in helpers.c that can
  be changed at compile time for those that really need it.
- No more 'splash' kernel commnand line option.  This turned out to
  be *very* confusing to many users who believed it was some sort of
  graphical splash screen à la Plymouth.

Also, when Finit debug is enabled we now have a global 'debug' flag
which now alo controls if klogctl() should be called to prevent the
kernel logs to the console or not.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

README.md

@@ -225,25 +225,6 @@ hook into the boot process or respond to various I/O.
 For more information, see [doc/plugins.md](doc/plugins.md).
 
 
-**Progress**
-
-Finit prior to v3.0 showed the progress at boot: plugins and modules
-being loaded, run/tasks/services being started, etc.  By default Finit
-is now silent, but progress can still be enabled at build-time using:
-
-    configure --enable-progress
-
-or at boot from the kernel cmdline using the boot parameter `splash`:
-
-```shell
-append="init=/sbin/finit splash"
-```
-
-For a really nice boot, add `quiet` as well.  This silences the output
-from the kernel, leaving only warnings and errors.  For other kernel
-command line parameters, see [doc/build.md](doc/build.md#recovery).
-
-
 **Automatic Reload**
 
 By default, Finit monitors `/etc/finit.d/` and `/etc/finit.d/enabled/`