Change freebox-switch to use Switch API

[LudovicRousseau]

The data for the 4 switch ports can be retrieved using the Switch API
https://dev.freebox.fr/sdk/os/switch/

No need to access the access the RRD database any more.
Also you get much more details: bytes in/out, packets unicast in/ou, packets multicast in/out, packets total in/out.

Old graph:

New graphs (for the same data)

If you agree with the change I will provide a PR that

• removes the old freebox-switch
• add the new freebox-swicth-bytes and freebox-switch-packets

The code is already working for me in https://github.com/LudovicRousseau/Freebox-OS-munin/tree/local

[LudovicRousseau]

Already merged upstream.