Create an If predicate

[p013570]

The predicate would have 3 fields:
'condition': boolean
'then': Predicate
'else': Predicate

We should also allow a 'predicate' field to be set instead of the 'condition'. The logic would then look something like:

boolean computedCondition;
if(null == condition) {
    computedCondition = null != predicate && predicate.test(input);
} else {
    computedCondition = condition;
}

if(computedCondition) {
    return null == then || then.test(input);
}
return null == else || else.test(input);

This should be similar to the way the Not predicate is implemented.

[p013570]

Merged into develop.