Restructure code layout, add make tasks

- Move source files to src/*
- Add all_firmwares make target which builds all firmwares
  utils/buildall.sh used to do this
- Add astyle task which runs astyle on src/*.h
- Add rules to the astyle config file
- Make all_firmwares the default make target
- Move utils/Astyle/* to bin and etc respectively
- Use astyle reformat with the new rules
- Put all temporary build files into out
- Rename the output firmware file to {tx,rx}-{board_type}.hex