PHP sensors are connected to WebApp Sensors.

The Apache sensors are renamed to ```webapp``` to maintain
the same name sensor.
A operation enricher are included in order to deduce values
among several sensors.

Some ```web.app.*``` sensors can not be connected to Apache Server:
```
webapp.reqs.bytes.received
webapp.reqs.bytes.sent
webapp.reqs.processingTime.max
webapp.reqs.processingTime.max
```