Replace magic number for M-Bus frame data length with define
Add new function to send a user data packet from master to slave
Move event handling from global variable to handle
- remove global event function pointer
- add event function pointer to handle structure
- add handle parameter to register functions
- move all register functions to mbus-protocol-aux.c
Fix event handling after moving callbacks to mbus handle
Merge pull request #60 from lategoodbye/master

Improve event handling and support to send user data