add log level to log message
remove debug code
chomp system('uname -a') output
remove eskk#logger#{error,errorf}()

Use the following functions instead:
* eskk#logger#write_error_log_file()
* eskk#logger#warn()
* eskk#logger#warnf()
output lines to cmdline if writing to a file fails
write pressed char to debug log
add eskk#logger#infof()
doc: fix description of g:eskk#log_file_level

Add note about error log message.
The change introduced in
commit 24cccdf9f91a7c6f8da15c1f9c675ba040826d48.
Merge branch 'master' of ..\..\_misc\eskk.vim into multi_dictionary