Finalized UART fix.

- UART buffer is now explicitely cyclical in transmission (Tx)
- Size of UART transmission and reception buffers can be adjusted through defines in uart.h directly. Supports until 2^16 bytes in buffer length (practically the whole ram) per buffer (Rx and Tx)
Topology feedback implemented

Note: topology has wierd values, the transmission mechanism was tested and was ok if other values were supplied. This could be a bug with the topology code.