Feat Don't log to stderr / stdout

[M3ssman]

Description

The main rationale behind this PR is to replace any usage of System.err.println or System.out.println by a dedicated Logger to be able to persist those information for later investigation in case of errors.

The Logging uses slf4j-api and the implementation of ch.qos.logback , since the latter is preferred by the spring framework which is used throughout the actual service implementation.

Sample logging configuration included at src/main/webapp/resources/logback.xml.

[M3ssman]

The subsequent commit handles a strange effect when LAREX_VERSION is not set in environment, since this isn't the case in our context. Btw, how do you set this? At Tomcat startup?