Fixed maven build:

 - Updated izpack version from 5.0.0-rc2-SNAPSHOT to 5.0.0-rc4:
   - Maven build failed because rc2-SNAPSHOT wasn't available in the snapshot repository anymore.
   - Removed references to the codehaus snapshot and release repositories as izpack now resides in the central repo
   - There is probably still an issue executing the installer as described here (https://github.com/taconaut/pms-mlx/issues/74) (not tested)
 - Updated maven plugin versions to fix maven site generation as described here (https://cwiki.apache.org/confluence/display/MAVEN/AetherClassNotFound)
 - Added pluginExecutionFilter to avoid eclipse displaying errors in the pom.xml
 - Properly formatted pom.xml

Configuration tested with maven 3.2.3 and java 1.7.0_67 with an empty local m2 repo using the commands:
mvn com.savage7.maven.plugins:maven-external-dependency-plugin:resolve-external
mvn com.savage7.maven.plugins:maven-external-dependency-plugin:install-external
mvn clean package -P osx -P linux site