Reorganization of the forum categories

As a follow-up to our decision to restart the DS-015 effort under the management of the UAVCAN Consortium, the following changes have been implemented:

The new UAVCAN Drone Application Layer will be developed between the UAVCAN Consortium members only. To become a member, please follow the instructions given at Note that major open-source projects, non-profits, and registered academic institutions are entitled to free membership.