Renaming types&functions,checks handle errors,validate takes init list

Several types & functions have been renamed. Checks now get the info whether an error occured and return boost tribool instead of bool, the third bool state being "error".
Thus the check decides whether to swallow the error or to return "error". The condition can then decide what to do if the check returned the error.
validate now takes init lists & vectors, but no variadic parameter lists.