logs: hide timestamp by default

[532910]

while prepending log lines with timestamp may be a good feature, it must be disabled by default, the same way as all other programs do

[AnnaShaleva]

An option should be added, but it's under discussion whether to enable this option by default. To me, it should be explicitly enabled by the node user if needed, otherwise the original behaviour should be preserved.

[532910]

it's ok with controlling terminal, otherwise — no

[532910]

It's ok to print timestamp by default, if the program is intended for developers.
In case it's intended for users -- the default should be not to show timestamps.

[roman-khimov]

void syslog(int priority, const char *format, ...); suggests that time is not something app should manage, but it's not often used these days. Current standard way to handle logging is to just print things to stdout and let journald handle it. Developers love stdout as well, so there is a conflict. Checking tty for it is an interesting proposal, but I'm not sure everyone would like it. More opinions on defaults/autodetection are welcome.

[EESergey]

Advanced logging with application timestamps can be output in debug mode. By default, debugging mode should be disabled. As an option, enable debugging mode depending on the application version; it will be enabled on pre-release versions.

[532910]

I would not like to receive additional timestamps when enabling debug logging.
It should be a separate control or presence of controlling terminal.

[roman-khimov]

Level is orthogonal to format. For now I tend to think that tty magic is the best way to handle the problem.