New rules regarding namespaces used as values

The following patterns are considered not warnings:

``` js
import * as foo from "./foo";

foo.bar();
const baz = foo.baz;
const {property} = foo;
```

The following patterns are considered warnings:

``` js
import * as foo from "./foo";

foo();
const [value] = foo;
func(foo);
func(...foo);
const alias = foo;
const {child} = foo; // foo.child is an exported namespace
```

---

Basically, warn if a namespace is used in a way that cannot be validated (aliased, called, destructured as array, passed as argument, etc.). There's no overlap with [`namespace.allowComputed`](https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/namespace.md#allowcomputed) in the above, but that option could be merged into this one, or these merged into another `namespace` option.

Review the existing namespace rule and its namespace.allowComputed option, then compare each listed usage against the requested warning behavior. Decide whether this belongs in a new option or a merged namespace option, and verify that accepted patterns remain non-warnings while unverifiable uses produce warnings.

Written by the indexing model from the issue text.