Logging

This adds a Logging "library" to the ECSS Services repo. This library allows logging messages with different severities, and allows the user of the services to choose which severity they want displayed.

A comparison between Google (glog), spdlog, plog and Boost::Log was made, and we decided to go with a custom lite solution, also compatible with etl::string.

The following log levels are supported, but they are up for discussion:

Level	Description
trace	Very detailed information, useful for tracking the individual steps of an operation.
debug	General debugging information.
info	Noteworthy or periodical events.
notice	Uncommon but expected events.
warning	Unexpected events that do not compromise the operability of a function.
error	Unexpected failure of an operation.
emergency	Unexpected failure that renders the entire system unusable.
disabled	Use this log level to disable logging entirely. No message should be logged as disabled.

The library uses #defines that allow logging in this way:

LOG_ERROR << "Configuration not found";
LOG_INFO << "The camera took " << 15 << " pictures today";
LOG_DEBUG << "Ran function " << functionName << " with " << getId(functionName);

Closes #18 (closed).

It is lite enough to be used on a microcontroller.

See https://acubesat.gitlab.io/obc/ecss-services/docs/logging/classLogger.html for more detailed documentation of the Logger functionality.

The following images show a sample log output on x86 and on an MCU via UART: