Dervishes are not a sect. They are student initiates in sufi orders. Sufism is not a sect either; they are brotherhoods/sisterhoods that Muslims (and occasionally some Christians and Jews) belong to. The definitions you cite are at best incomplete. The fellow in the photograph is more likely a circus performer than a sufi dervish.
I am very pleased, however, to see that you're taking the time to learn more. Keep it up, and I'm sure we'll see less inaccurate/xenophobic statements from you. If you really want to understand what it means to be a dervish, check out the aforementioned
http://www.sufism.org and
http://www.uga.edu/islam/ (written by U of Georgia professors). It's fascinating stuff. The latter is an incredible source of information, from an American perspective.