Exclude slf4j binding from library

[twagoo]

The pom-file declares dependency on the slf4j logback binding. This can be problematic when using the toolkit as a java library. Suggestion: make a build profile for the conversion tool and define the log bindings in that profile only.

[benhur1999]

Another idea: split library and conversion-tool in two artifacts and only add the dependency to logback to the tool. The library, of course, needs a dependent on slf4j-api (which is fine, IMHO).
It's handled in a similar fashion in the cmdi-validator