Support multiple checkstyle executions

Multiple execution sections may be defined in pom.xml e.g. in order to
provide different rules for unit tests and production code.
Plugin Wrapper contains multiple MoJo executions. A file set and config
is created for each one.
Findbugs and PMD throw an error if more than one MoJo execution is
found.
Add example project
Fix file locations
Remove obsolete parameter
Merge branch 'multiple-checkstyle-executions' of https://github.com/tinexw/m2e-code-quality into tinexw-multiple-checkstyle-executions

Conflicts:
	com.basistech.m2e.code.quality.findbugs/src/main/java/com/basistech/m2e/code/quality/findbugs/EclipseFindbugsProjectConfigurator.java
	com.basistech.m2e.code.quality.findbugs/src/main/java/com/basistech/m2e/code/quality/findbugs/MavenPluginConfigurationTranslator.java
Remove unused parameters
Correct build.properties