Fix warning on GCC 7.3

bug fixed in db_manager by adding add_wave by id

Merge branch 'master' of github.com:robotsthatdream/cafer

change db_manager to allow adding new waves during experiment

Fixed db manager so its status is set to false when buzy

clean up and ad wave metadata saving at the instantiation of _DBFileSystem

bug fixed : descritor -> _descriptor

Merge branch 'master' of https://github.com/robotsthatdream/cafer

adding the supervisor header file to be part of cafer core

Cleaned up README.md

Merge pull request #29 from ghanimmukhtar/patch-2

Update README.md

Update README.md

Update db_manager.hpp

Minor fixes