return types in CriteriaBuilder

It would be nice if operations of `CriteriaBuilder` returned `NumericExpression`, `TextExpression`, `TemporalExpression` where appropriate.

A problem is that we have operations like this:

```java
Expression sum(Expression x);
```

and I would have to add an additional type constraint:

```java
> NumericExpression sum(Expression x);
```

That's in principle a backward incompatible change ... but I can't actually see it breaking real code, so perhaps it's OK?

Review the CriteriaBuilder method signatures shown in the issue and the open linked pull request #1005 first. Done means the intended NumericExpression, TextExpression, and TemporalExpression return types are defined consistently and the backward-compatibility concern is resolved.

Written by the indexing model from the issue text.