Explicitly add `.cpp` sources to get_sources
Remove hardware version 1 code from feedback
Measure peak-to-peak instead of mean voltages
Do not import `DMFControlBoard` in `__init__.py`

Do not import `DMFControlBoard` in `__init__.py`, since this prevents `paver`
from running its first pass, due to a circular dependency _(the
`dmf_control_board.protobuf_commands` module is only generated by running
`paver copy_nanopb_python_module`)_.
Fix nanopb Python code generation issue due to...

Fix nanopb Python code generation issue due to Protocol Buffers Python library
version.