Extension of import format for attributes in explorer

[mirschel]

Present format see header of org.mpg.dcts.promot.viznav.data.io.AttributeReader.java

For future work we need a way to encode parts of hyper edges not only the whole hyperedge, e.g. TargetNode <tab> SourceNodeX <tab> SourceNodeY <specialtab> SourceNodeX <tab> !AttributeValue1 <tab> !AttributeValue2 <tab> AttributeValueN

The row above means we have attributes for the construct 'SourceNodeX (AND, OR) SourceNodeY results in TargetNode'. The second occurrence of SourceNodeX means that we want consider only the edge from SourceNodeX to TargetNode, thus only one part of the hyper edge. The edge from SourceNodeY to AND/OR will not be considered.