bugfix in OperationNode copy constructor
added a new method: OperationNode.setTotalUsageCount()
minor changes to some models used in tests
disabled distillation model usage in pattern detection tests (takes too long)
increased precision of printed values in the source code used by the pattern tests
improved plugflow model(s)
fixed issues related with some temporary being determined for iterations where they are not used
minor changes to comments
replaced assert() with a new #define CPPADCG_ASSERT_UNKNOWN()
bumped version to 1.4.0