Using comma-separated list of globs to set files to include and exclude

A set of files to be validated can be defined using lists of globs with patters to match against files to be included or excluded from validation, like
```
<!-- Comma-separated globs of files to be validated -->
<includes>src/**/*.java, **/*.xml</includes>
<!-- Comma-separated globs of files to be excluded from validation -->
<excludes>target/**</excludes>
```