0.5.0

changelog:

- removed `SENS` command
- repurposed i/o module for global obstacle detection and battery
  monitoring (latter not yet implemented)
- allow client to send `W2_M_PREV` using `w2_send_mode()`
- implement error logs in client
- implement order entering in client
- implement manual mode switching in client
- handle more error/warning types
- fixed client tab flickering
- updated client/readme
- new `w2_newline_count` function in shared/util.h