Merge pull request #1 from dashdashbang/master

Pull request for Joris' first commit, as we discussed in the chat
FRE - fixed copy & paste mistake with self.startVideo (but second request was ignored anyway)
added lesson 6 (rather work in progress)
added Lesson 6 into overview (and text revision)
simplified "installation" (lessons 3-6)
revised lesson 1 (flying code moved to lesson 2)