Retrieve signal lists from IC status updates and store them in the DB

[stv0g]

This could be used by the IC configurations to auto-import the signals.

Related to #87.

[stv0g]

I have updated the VILLAScontroller protocol documentation to include a signal list as part of the IC properties:

https://git.rwth-aachen.de/acs/public/villas/documentation/-/blob/master/docs/controller/protocol.md#L206

The format is the same as used by VILLASnode for its signal descriptions.

[stv0g]

The relevant issue for VILLAScontroller is: https://git.rwth-aachen.de/acs/public/villas/controller/-/issues/40

[stv0g]

Related: https://git.rwth-aachen.de/acs/public/villas/controller/-/issues/41