added pattern tableau for conditional unique column combinations

added pattern tableaus as display type for conditional uniques

Small fix in ColumnCombinationBitset where a ImmutableList was expected but the current Implementation is a List. Missing change after refactoring in the main repository.

Add a clone() method for PositionListIndex, which is a deep copy.
Do you have an idea how this can be platform independent? System.lineSeparator() and System.getProperty(line.Separator) do not work because GWT compiles this code in javascript and there is no javascript equivalent for these method calls.