- removed obsolte txamp functions (re DAC enable sequence)
- reorderd TX enable sequence
- consolidated time keeping (ticks/time vs sample count)
  - added RX_ and TX_ prefixes for samples counts
  - added new data type rx_sample_cnt_t
  - renamed function to calc rx lag for more clarity
  - deactivated downsampling (locked feature, almost all steps made)

- moved I2C configuration to board_config.h
- introduced constants in board_config.h for all IRQ priorities
- aligned values of IRQ priorities

- dropped support for OLD TXB with MCP4551 (see ERRATA)
- added support for NEW TXB with AD5245
- added timeout for busy-waiting peripheral (UART, I2C, SPI) interaction; on timeout, the MB indicates an error state through LEDs
- updated AD5245 interface/driver to support two devices (distinguished through A0 bit)
- tweaked TX/RX switch sequencing

changed implementation of tx-gain setting/handling  (now set upon enabling the TX board), because new TXB (v5 and newer) disables poti when inactive (off)

changed interface of txgain (appended Level, added function to obtain number of tx gain levels, added number of gain levels to ACI response

fixed a bug that accidentally included (empty) sim bootloader instead of platform bootloader; stripped down makefile and removed stm-legacy makefile alltogether; yet need to shift stuff from platform makefiles to generic one