ENH-6 change name of project

[peterborkuti]

Project was named after opencv_haartraining and opencv_createsamples, but haartraining is obsolete now. Users should use opencv_traincascade.
(This is unrelated to the usefulness of this project, it impacts only the name)

Candidates are:
objectlabeler
imagelabeler
samplelabeler
prepareimages
preparesamples