Reworked forwarding capabilities and logging

[channels]
- check buffer_unused in receiving
- don't send empty buffers
- call on_close callback

[conf]
- call tunnel_close callback
- check for configured tunnels before creating outputs

[forward, tlv]
- properly generate some tags

[logging]
- print offset in hex
- fixed bug in multiline hexdumps

[main]
- removed obsolete comment

[pbuffer]
- use buffer_start for growing
- made some macros static inline functions

[portall.conf]
- added tags to inputs