npe bug fix.
Merge branch 'master' of github.com:3drobotics/3DRServicesClient into dp_3dr_services
update to the drone event registration interface.
Merge branch 'master' of github.com:3drobotics/3DR-Services-Library
refactoring of the client api.
disable automatic start of the drone api.
Merge branch 'master' of github.com:3drobotics/3DRServicesClient into dp_3dr_services
improve visibility into the drone started state.
Merge branch 'master' of github.com:3drobotics/3DRServicesClient into dp_3dr_services
3dr service disconnection bug fixed.