Update licence to GPL/LGPL
Utilization of AMiRo-OS in other projects should be made easier by relaxing the license requirements from GPL to LGPL. Because AMiRo-OS depends on ChibiOS, which is licensed under GPL, AMiRo-OS must still be available under GPL as well, so a dual license approach is desired. In case the dependency on ChibiOS can be relaxed, AMiRo-OS should be available under a slightly less strict license as well: LGPL.