driver pigcs: improve IP scanning

Don't fail if no internet access is available. Instead, just broadcast on
each interface.

The only drawback is that it bring a new dependency on package netifaces.
driver pigcs: scan for controllers over IP

Still needs proper testing.
driver pigcs: add tests for IP
config: update dependencies

need opencv >= 2.4 for circle detection (on Delphi)

need netifaces for pigcs over IP (autoip feature)
driver pigcs: fix name of actuators found via IP scanning