set properties for versions for slf4j and log4j 2
Local configurations within plugins should be avoided. Where plugins do not pick up default
properties already, they should be injected manually into the plugins.
-->
+ <slf4j.version>1.7.22</slf4j.version>
+ <log4j.version>2.8</log4j.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.target>1.8</maven.compiler.target>
<maven.compiler.source>1.8</maven.compiler.source>
