Fix kotlin-gradle-plugin to correctly process java source files

Do not remove outdirectory from cp in maven: this is needed for gradle-plugin build to see files compiled by gmaven
    this may cause problems with running mvn install without clean for kotlin
Remove special magic with groovy-output in gradle-plugin pom.xml

libraries/tools/kotlin-gradle-plugin-core/pom.xml

@@ -78,9 +78,6 @@
             <resource>
                 <directory>${project.basedir}/src/main/resources</directory>
             </resource>
-            <resource>
-                <directory>${project.build.outputDirectory}/../groovyOutput</directory>
-            </resource>
         </resources>
 
         <plugins>