bounded and unbounded are not antonyms

If we assume finite == !unbounded in assumptions, we
create an alias: finite=False is the same as unbounded=True
and vice versa. We don't want to do that. What we want is
behavior like integer and noninteger:

Dummy(integer=0) is not the same thing as Dummy(noninteger=1).
A noninteger is commutative, complex, hermitian, noninteger,
nonzero, and real while integer=0 is only commutative -- nothing
else is known about it (other than that it is not 0).

/!\ In general, it is much easier to comprehend what one means
by using only true attributes to desccribe it. If something is
not zero but still complex, say nonzero=True instead of zero=False.

So assumptions.py has been modified to make the following true:

```
finite   : 0 < abs(x) < oo
bounded  : 0 <= abs(x) < oo
unbounded : abs(x) == oo
```

The same is also true for zero and nonzero. If nonzero is True you
are talking about a complex number that is not zero. But if zero is
False you are only talking about a commutative object that is not
zero.
Mul._eval_is_rational watches for real and zero