repository layout seems to have strong Java Maven bias

[sophokles73]

The proto3 files are currently all kept under src/main/proto which seems to be due to the fact that this is the standard Java Maven project layout and Maven is used in the CI job to verify that the protos are valid (aka can be used to create and compile Java code from them).

As suggested here I propose to move the protos to the top level of the repository because this repo's whole purpose is to provide a home for the uService definitions themselves (not any accompanying Java code).