[IMPROVE] Add documentation section Log and Alarmas

[cesarjorgemartinez]

Add documentation section Log and Alarmas

As other Fiware components, by example https://fiware-orion.readthedocs.io/en/master/admin/logs/index.html

[AlvaroVega]

Alarms doc is in: https://github.com/telefonicaid/fiware-sth-comet/blob/master/doc/manuals/alarms.md
PR for fix alarm doc link: #448

[AlvaroVega]

Logs docs is included in
https://github.com/telefonicaid/fiware-sth-comet/blob/master/doc/manuals/running.md

LOGOPS_LEVEL: The log level to use. Possible values are: "DEBUG", "INFO", "WARN", "ERROR" and "FATAL". Since the STH component uses the logops package for logging, for further information check out the logops npm package information online. Default value: "INFO".
LOGOPS_FORMAT: The log format to use. Possible values are: "json" (writes logs as JSON), "dev" (for development, used when the NODE_ENV variable is set to 'development'). Since the STH component uses the logops package for logging, for further information please check out the logops npm package information online. Default value: "json".