* nx.tcl, parameters.test (defineIncrementalOperations): Make sure value=add and value=delete actually run value checkers and, in case of "convert", pick up the conversion result. Added basic test.
* nsf.c (ArgumentCheck): Avoid double dispatching to value checkers (built-in and type=*) for "slotset" parameters. Previously, configure and then the value=set (value=add) method triggered one dispatch each. Now, the configure pass skips the check and shifts sole responsibility on the value=set/ value=add methods. Added basic test cases to parameters.test to capture the intended call semantics.