Add (client only) support for rda3

[wirew0rm]

This adds support for RDA3, the protocol used by CMW/FESA based devices.

• Fixes some quirks in the cmwlight serialiser that are needed to serialize the control messages:
  • support for maps
  • deserialise empty objects/maps
  • some minor bugs
  • add unittests with real world data to prevent regressions
• Adds a lightweight zeromq STREAM based nameserver client to resolve rda3 device names
• Add a cmwlight client implementation

There are still some open points, for now only get requests are handled completely, subscriptions generally work but need a bit more state-tracking to be reliable

• [ ] finish the state machine
• [ ] replace some fixed strings with the actual data (e.g. client information)
• [ ] integrate the name server into the client.
• [ ] general code cleanup