caosdb-client.json is still kept, but linkahead has precedence.

TODO: Add tests checking support for caosdb_client.json

Fix compilation errors on Windows

See merge request !48

- add generated protobuf source directory to global include folders

On Windows this does not compile without. On Linux, it should not hurt.

Linking against caosdb should achieve the same.

This is experimental.

Add vcpkg support

See merge request !53