Sort out Protobuf in our repository

[Levi-Lesches]

So far, the plan is to have two separate repositories.

• rover-api: holds the .proto files for all possible rover messages
• rover-network: holds the C++ and Dart networking libraries, including a wrapper .proto file

We need to

• include the rover-api proto files in our implementation, and store the generated code under lib/src/data/messages
• import the rover-network library, which should already include the generated WrapperMessage class.

[Levi-Lesches]

Alternatively, we can have one networking repository rover-api that just holds all the .proto files. Then, we can store our Dart-specific networking code in lib/src/services/networking and the generated message classes in lib/src/data/messages. The C++ library can then stay in its own relevant locations. This would simplify our structure since

1. We won't need to import a repository that's half C++
2. We anyway need some networking code in our lib/src/services folder, even if we import most of it

[Levi-Lesches]

Being tracked in BinghamtonRover/Protobuf#1