Migrate commons.logging and log4j-1 loggers to SLF4J

[HannesWell]

This is a draft of the work to unify the logging frameworks used in MWE to use only slf4j and at the same time to migrate off commons.logging and log4j-1.

Currently this only contains the changes in java-code and the removal of the then obsolete logging frameworks from the target-platform, features, etc.

What's missing is the migration of the (log4j-1) configuration and the addition of a logging back-end slf4j can use.
My suggestion is to use slf4j-simple as a back-end.

The changes to adapt the projects that contain workflows to generate for example xtext DSLs are also missing because I don't know yet where to change that.
Furthermore the log4j.properties have to be migrated to the back-end chosen eventually. E.g. for slf4j-simple the doc is:
https://www.slf4j.org/api/org/slf4j/simple/SimpleLogger.html

This would help to solve eclipse-xtext/xtext#3127 at MWE side.

@cdietrich what do you think?

[cdietrich]

I have no capacity to think currently

my problem is that such a solution has to work ganzheitlich.
Also with Xtext consuming mwe
How new Xtext project wizard creates stuff
How stuff is logged if you execute from
Maven gradle launch config in eclipse etc

[HannesWell]

my problem is that such a solution has to work ganzheitlich.

Sure. I was already thinking about enhancing the MWE2 launcher to automatically add the additional bundles required to run the worklow, that are currently defined as 'development'-bundles using additional.bundles in the build.properties.

This would have the advantage that

1. these definitions in the build.properties are not necessary anymore
2. the requirements (like in this case) can be changed easily, only the launcher has to be adapted.