CUL transport and bindings for Intertechno, FHT, FS20, EM and S300TH

This is pull request for review. It contains a CUL transport bundle which handles communication with culfw based devices (culfw.de). Currently only serial devices are supported, but implementing network based devices shouldn't take much effort.
The bindings for FHT (heating control), FS20 (Switches, Dimmers, Contacts etc.) and Intertechno (Switches) seem to be working flawless for months. The S300TH bindings is tested by Holger Heems and seems also to be working for weeks now. The EM bindings should be considered experimental. It is an implementation after specification without test on real devices.