Add init logs and improve log traces

[mapedraza]

Describe the solution you'd like

Add initial log block and make it independent from log level (always printed). Improve log traces

[AlvaroVega]

Current log levels provided for logops are 'DEBUG', 'INFO', 'WARN', 'ERROR', 'FATAL'

https://github.com/telefonicaid/logops/blob/5310b7516caf857ef4ecafc966fe8f9e9f77db81/lib/logops.js#L19-L20

Maybe we can still use any of these levels ( FATAL or ERROR to ensure log is always procuded) and include any new string like "INIT" at log statup

[fgalan]

It would be great to check with Operations that a new INIT loglevel is ok with them. For instance, the log management tool could be ignoring all except the classic 5 ones.