Convert and delete some old API tests

Remove the following modules:

1. `test_computeresource`
2. `test_configtemplate`
3. `test_domain`
4. `test_environments`

The first three contained no working tests and no interesting test stubs. The
existing test stubs were for goals such as creating or deleting an entity. Given
that all four relevant entities are already tested in module
`test_multiple_paths`, there is no value to the stubs.

The fourth module contains tests for creating environments with valid and
invalid names. Port these tests to module `test_environment_v2`.

Remove outdated module references from the API documentation.
@omaciel, the old API tests explicitly tested for this behaviour. I've written these new tests to enforce the same behaviour. Here's the relevant snippet of old test code:

```python
@data(
    generate_string('alpha', 256),
    generate_string('numeric', 256),
    generate_string('alphanumeric', 256),
    generate_string('utf8', 8),
    generate_string('latin1', 8),
    generate_string('html', 8),
)
def test_negative_create(self, name):
    ...
```

>  is it by design or because it is a bug?

I have no idea.