Added possibility to skip pipeline in cause of failure during transformation #56. 
Extraction can go to multiple graph or into one graph.
Log is used instead of event to report 'extraction problem', #35.
Merge branch 'develop' of https://github.com/UnifiedViews/Plugins into develop

Conflicts:
	t-filesToRdf/pom.xml
Merge branch 'develop' of https://github.com/UnifiedViews/Plugins into develop