Generic host components for Nugget

Nugget will be used in different contexts and with different hosts. This repo contains the components that can be shared between those hosts.

`nugget`

The nugget directory contains items that are shared between the host and the firmware. Those include:

shared headers
service protos

`libnos`

libnos is a C++ library for communication with a Nugget device. It offers an interface to manage a connection and exchange data and a generator for RPC stubs based on service protos.

`libnos_datagram`

libnos_datagram is a C library for exchanging datagrams with a Nugget device. This directory only contains the API of the library as the different platforms will need to implement it differently.

`libnos_transport`

libnos_transport is a C library for communicating with a Nugget device via the transport API. This is built on top of the libnos_datagram library for exchanging datagrams.