Don't use relative imports like `../foo.h` as those depend on the
relative position of both files. Rather than that use imports relative
to the `src` directory, which explicitly is part of the include
directories.
Instead of casting the UUID object to the ble_uuid_t* used throughout
the NimBLE API just pass the address of the ble_uuid_t member that's at
the start of each of the UUID structs.
