Interest for sensor related feature

It could be helpful to expert and operator to be able to work easily with everything related to sensors.

In particular it would be helpful to retrieve the list of floats equipped with a given sensor.

this could go like this:

```python
from argopy import ArgoSensor

# Return the list of sensors from reference table R27
ArgoSensor().list()

# Return all sensor names with 'SBE' string
ArgoSensor().search('SBE')

# Return list of WMOs equipped with a sensor having the 'RBR' string
ArgoSensor().read_wmo('RBR')
```