#1116 PMD Eclipse plugin doesn't analyze project if it has non-existing source folders

[Andreas Dangel]

Found while upgrading m2e-code-quality plugins. If you import a maven project, the eclipse configuration for the project adds all source folders (src/main/java, src/test/java) even if they don't exist.
Even if this is maybe a wrong project configuration by the m2e plugin, the PMD Eclipse plugin should simply ignore this non-existing folder and continue analysis.