all services: use ConfigItem instead of deprecated ConfigurationItem

The class `ConfigurationItem` from AstroPy is deprecated and will be removed in version 1.0
I think this shows that it works correctly?
```
>>> from astroquery import vizier
>>> vizier.conf.timeout
60
>>> type(vizier.conf.timeout)
<type 'int'>
>>> v1 = vizier.Vizier()
>>> v1.TIMEOUT
60
>>> vizier.conf.timeout = 42
>>> v1.TIMEOUT
60
>>> vizier.conf.timeout
42
```