Services to clone and to flush raw data

[ffleurey]

When using raw sensors we often want to save a subset of the data to a new sensor and delete the rest of the data.
To do that we need 2 services:

• A copy service which allow copying the data from a sensor to a new sensor. We should be able to specify as parameters a start and an end date.
• A delete service which allow removing all the data from a sensor between a start and an end date.

In the admin these services can be used to have "clear data" and a "clone sensor" buttons for every sensor. A more elaborate version could allow specifying the start and end dates but this is not really needed in the admin.