knxproj - KNX project parser

I ported an existing project parser from Java to Go, which resulted in a bit of an ugly code.

Export used devices as JSON: go run cmd/main.go Project.knxproj

TODO

Test with two level group addresses.
Test against all knxproj files.
Sort addresses into a nice tree.
When converting address to string, respect the configured format.
Handle IsActive, somehow find out if device needs a full reconfiguration.
Improve json structs http://attilaolah.eu/2014/09/10/json-and-struct-composition-in-go/
Convert bit size without DPT, to a good dpt. 1bit = dpt 1. 2bit = dpt2, 4bit = 3.007
Study this project https://github.com/owagner/knx2mqtt