Add ability to use a function in an update statement

[jeffgbutler]

This also removes the incrementBy, decrementBy, etc. operations as they
are replaced by more flexible alternatives.

[coveralls]

Coverage remained the same at 100.0% when pulling af417bd on jeffgbutler:master into 549c458 on mybatis:master.

[tnicolas29200]

Hello,

it's interesting. It standardizes the use of arithmetic operations in queries.

Unfortunately, it is still not possible to use dynamic values (or i don't see how to do that).

With your implementation, you can't have something like :
UPDATE table SET field = field + xxx

where xxx is a dynamic value, like 1 or 3 or 15000.

You can just write 1 class per constants, so you must use a constant of the operand at design time and not passing a variable value.
I need to be able to parameterize a query with a dynamic value not recovered from a subquery or another field

[jeffgbutler]

You could write a generic function like this

    private UpdateStatementProvider generateUpdate(Integer _id, Integer factor) {
        return update(foo)
                .set(bar).equalTo(multiply(bar, constant(factor.toString())))
                .where(id, isEqualTo(_id))
                .build()
                .render(RenderingStrategy.MYBATIS3);
        
    }