Add buttons to highlight that error or warning messages were logged.

Fixes #106

With the new warn/error button, the user already is informed if
something important is logged. By only showing nearly all log messages
in the status bar, messages can be missed easily.
Fixes also an issue where the status bar was accessed before it was
initialized (crash with assert). (Fixes #299).

Tested with MSVC 2022, this is no longer required.

The console feature was not documented very well and was only used for a
few messages.