Added SingleRulesAlwaysTruePredicate and MultipleRulesAlwaysTruePredicate - resolves #116

Use SingleRulesAlwaysTruePredicate  instead of
org.projog.core.function.bool.True and MultipleRulesAlwaysTruePredicate
instead of org.projog.core.function.flow.RepeatSetAmount (as True and
RepeatSetAmount do not work with variable number of arguments).